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Eberspacher fault finding.
Faults are in a logical order, look down the list for the heading that matches your fault and begin there.
The commonest faults are also given on the Fault Finding Simple page.
Although there are many different fault causes listed the vast majority of heaters run without any problems, just needing a regular service. Derek has been relying on Eberspachers for his caravan heating for more than 12 years, with just a blower motor failure and minor malfunctions caused by bad fuel and an occasional loose or disconnected wire. We have never encountered most of the faults listed here.
If you have an Eberspacher controller with diagnostic readout use it, you can save many hours of investigation time.
It may be worth considering changing your controller to one with diagnostics like an 801, 701 (blue logo version), or EasyStart Select (check compatibility), details of these are on the Controllers page.
We have an improved / corrected version of the diagnostic fault codes from the manuals on our Fault Codes page.
DO NOT wipe the fault codes without permanently recording them, this information can be valuable for anyone diagnosing problems.
Some serious faults lock out the heater for safety reasons, clear these faults before resetting.
Occasionally the diagnostics can mislead by pointing to components outside the ECU when the fault is actually within the ECU.Also the majority of the ECU must be working to send the diagnostic information to the controller.
Controllers like the 701 or 801 will become more common so we are adding fault codes when we update sections.
Most users still have controllers without diagnostics and these pages are primarily aimed at repairing many faults without them.
Levels of DIY ability vary and it is not expected that everyone will want to or be able to do all these tests.
In that case a visit to a dealer or service agent may be needed after eliminating some causes.
Some faults, particularly ECU and burner failures, may have to be identified by dealers or by substituting known good components.

This page is based on faults to Eberspacher Airtronic heaters, D2 D4 D5, but most of the general information also applies to other models including Eberspacher water heaters. We have started adding water heater pages to the site and this page will be updated in the future to incorporate specific water heater faults.
This is not an installation site so most installation errors are not covered. It is intended for maintenance and repair of heaters that have been properly installed and have previously been working ok.
Apart from needing a service the majority of faults on Eberspacher installations are not due to faulty components inside the heater.
Checking at what stage the heater fails will narrow down the causes, you can then jump straight to that section of the page to fault find. That saves a lot of wasted time.
During the start up phase many faults are detected by the ECU, the heater shuts down before switching on the glowpin and pumping fuel.
The timing details are for one of the Eberspacher D2 versions.  D4 and D1LCC timings are at the bottom of this page. Water heater details and timings are being added to their servicing pages.
Other models timings, fan speeds and start up checks can differ, but most general fault details will still apply.
Low voltage, Wiring and Fuel problems are covered in greater detail on separate pages.
Fault Finding 3 page shows an example of practical fault finding when we had fuel problems on our own heater.
Most faults are now adequately covered but that also means the number of possible fault causes listed here may be daunting. We are still learning especially with unusual problems, and adding details to the website.
Some faults will still require a visit to a dealer, there is no way we can identify or solve every problem for you here.
A multimeter will be required to test components and sensors. They are cheap, on ebay March 2014 new ones similar to the one shown were 2.70 post free. Alternatively DT838 at 4.21 or similar mutimeters have an additional temperature measurement range and a temperature probe, extremely useful for checking ducting problems. I have included pictures showing tests, click on the images to show the position of the range selection switch. Do not force the probes into the connectors, just hold them against the metal contacts.
All 12v references should be replaced by 24v for 24v heaters.
Read the disclaimer at the bottom of this page.
Airtronic D4 Normal start up sequence.

How the Eberspacher D4 heater should start if there is no fault and everything is working properly.
Stage 1 Switch on.
  When the Airtronic D4 heater is switched on, the indicator light in the control element illuminates showing the heater is on.
Stage 2 Pre start checks.
  The fan runs at medium speed, then drops to slow speed.
  Control unit does an electrical check of the glow pin, flame sensor, temperature sensor, fuel metering pump and control unit.
Stage 3 Preheat.
  Glow pin is energized at 5 seconds point and starts preheating the combustion chamber.
  Fan turns slowly.
Stage 4 Fuel on.
  At 60 second point pump starts at slow rate rate,  At 80 second point fan increases speed gradually.
  White smoke which is unburnt fuel may come from exhaust.  Ignition will take place as the fuel air mixture contacts the glow pin.
  When heater "catches" smoke stops and you hear a jet like noise which increases.
  Once the flame detector detects the flame, in the manual this is shown occurring at the 110 seconds point which is possibly typical, the glow pin is switched off after 80 seconds (190 seconds point in the example).
  After the glow pin is switched off fan speed increases to power setting until burner case reaches target temperature.
     However if the heater does not ignite within 90 seconds after starting the fuel pump the start is repeated.
     If the heater still does not ignite after another 90 seconds of pumping fuel, the heater is switched off,
     i.e. the fuel supply is off and the fan runs on for about 4 minutes.
  The heater is in the POWER stage with maximum fan speed, pump speed, fuel quantity and roaring noise.
  Once the heat exchanger reaches optimum temperature the Eberspacher switches into control mode, the pump rate and fan speed are controlled by the ECU to give the required heat output - Boost, High, Medium, Low or Standby.

When the Airtronic D4 is switched off, the fuel pump stops and the glow pin is switched on for 30 seconds to clean off any combustion residues. The fan speed gradually reduces, it continues to run for 4 minutes to cool the heater.
If the heater is restarted and the heat exchanger is too hot the fan will run to cool it before restarting.

Airtronic D2 D4 Start up sequence common faults.
Faults are in a logical order, look down the list for the bold heading that matches your fault and begin there.

Stage 1 Switch on
When the Eberspacher D2 or D4 heater is switched on it is completely dead, nothing happens.
If the controller light or the display for some controller types is on go to the next heading.
The most likely problem is no power.
Check for blown fuses- there may be one at the battery supply point and possibly two on the end of the wiring loom, poor electrical connections, wire disconnected or a discharged battery.
Remember a fault on the negative battery supply wiring causes the same problems as one on the positive supply.
If the voltmeter and wiring modification described on the Low Voltage page has been done the voltmeter will confirm the presence or absence of power, otherwise check for 12v on the D2/D4 connector between pins 1 and 10.
Glow pin.   Fault codes 20, 21, or 22.
   Disconnect the black connector with the brown and white wires from the ECU and check the glow pin resistance.
   Eberspacher say a glowpin should measure between 0.42 to 0.7 ohms for a 12 volt heater, (1.2 - 2.0 ohms for a 24 volt heater).  [In practice the switch on check will only fail if the value is considerably different, sometimes several times the value]
   If you do want an accurate reading resistance values this low can be tricky to measure with a multimeter because of the resistance of the test leads and connections.  It is usually easier to connect the multimeter probes together and take a resistance reading. Then connect the probes to the glow pin connector and the reading will increase by the resistance of the glow plug.
   There can be an error of up to .1 ohms in the value measured so between 0.3 and 0.8  ohms is probably ok.
   In most cases a glow pin will fail open circuit which is easier to measure. The meter would then give an out of range indication (  1    . )
   Airtronic D2 and D4 glow pin failures are rare, older type glow pins burning out and failing open circuit are a fairly common fault. Eberspacher say do not connect D2 D4 glowpins to a 12v battery to test as they may burn out, they are marked 8v. In practice users say they have done so without problems, on normal voltage they glow red hot, on 12v probably orange. Keep the test short and remember health and safety, keep it away from anything flammable.
   Knobbly deposits on the glow pin usually indicate water in the fuel.

The three plugs connecting the overheat sensor, flame sensor & glow pin to the ECU.
They can be accessed by removing the D2 top cover and then releasing the ECU fixings.

Airtronic Combined Flame and Overheat sensor wiring.

More faults are listed in the fault code table in the manual, these two can also be checked out.
Diagnostic cable short circuit.    Fault code 025 new generation ECU only.
   The blue / white wire in the loom is only used for diagnostics, check it is not shorting out.
External temp sensor short circuit.    Fault code 061.
   The Eberspacher normally uses its internal temperature sensor unless it detects an external sensor.
   Disconnect the external sensor and it will be ignored at the next restart.

There are fumes or a mist from the heater when in use, especially just after switch on.
There is often a smell during startup especially if the heater does not fire immediately.
This is normal but if it persists do not ignore these problems, there are safety issues.
Unburnt diesel may leak onto the lagging. Check fuel pipes especially clips and rubber sleeve connectors which can become porous.
Often the cause of fumes is a loose exhaust joint or a fracture in the pipe. Exhausts are often lagged, concealing the leak.
Vehicle type silencers are not gas tight and must not be mounted in enclosed spaces. Click here for details.
The burner gasket may have failed allowing exhaust gasses into the heating air.
[Eberspacher exhaust gasses are not pleasant and should be avoided but should not be lethal, there have been no recorded deaths caused by them. Carbon dioxide levels are generally 9-12%. Carbon monoxide is normally about 39 ppm but can vary from 10 ppm to 150 ppm, levels between 100 and 200 ppm can cause a headache.]

The Eberspacher heater runs normally for 1 hour then switches off, it cannot be restarted for another hour.  No fault code.
This is usually an ex BT heater, these were restricted to 1 hour maximum heating time.
   Our D1LCC had a 1 hour timer in a black box plugged into a 3 pin connector on the loom.
   Remove the timer unit and connect the purple wire from the rheostat to the yellow wire on the 3 pin plug to bypass.
   A photo of the loom modification is on the Eber wiring page.
BT D2s were fitted with a 701 timer with a 1 hour maximum, no continuous operation and no diagnostics.
   See the Controllers page for a partial workaround for the 701.
The Eberspacher heater runs ok on slow setting but fails on high.
A second hand D1LCC bought on ebay overheated and shut down after about 5 minutes whenever it switched to high setting.
A pumped fuel volume test showed pump was giving too much fuel, the buyer then identified heater had been sold with a D2 pump.
(http://users.aber.ac.uk/nns/eberspacher/eberspacher%20tale%20of%20woe.html gives the full story)
Fuel feed may be restricted so insufficient fuel reaches the heater.

The Eberspacher heat output is lower than it used to be.
ie the heater has been working fine but now with no changes to the installation it does not produce enough heat.
  a) heat output is ok if controller setting is increased. See also The heater drops down to low heat prematurely section.
     Heater thinks temperature has reached required temperature.
     If a remote sensor is fitted has anything generating heat been placed below it.     
     Check the obvious, blocked or damaged air ducts, inlets / outlets closed or obstructed, windows left open, temperature set too low.
  b) low maximum heat output.
     Check the items in part a)
     Give the heater a full service, don't forget to clean the vent hole and to replace the glowpin screen.
Low heat output with no or low levels of smoke leads to suspicions of low fuel quantity. Do a fuel quantity test.
Check fuel lines for air leaks, blockages, kinks or compression. Check fuel filter in the pump.
Check the rubber connecting pipes, when they deteriorate they can become porous or swell.
Air bubbles trapped where joints do not butt together and pieces or flaps of rubber shaved by sharp tubing can cause unseen obstructions. Fuel may have partially solidified in very cold conditions. Small droplets of water may have frozen in the pipes.
Check the pump has not moved into a horizontal position because of loose fixings or being knocked.
Unburnt fuel will usually produce smoke instead of heat and may smell, restrictions of combustion air or exhaust could be the cause.
(After a flameout or unsuccessful start some unburnt fuel may be present so that can also cause a smell.)
Fuel may have deteriorated or may simply just be non winterised or unsuitable. (See fuel pages)
Check the heater is reaching boost or high settings. (Fan and pump speeds will confirm)
If all these are not the solution think about what is happening  to get clues as to where to look next.
If combustion air and fuel are properly mixed in the right proportions and burnt then heat is produced which has to go somewhere.
If it does not come out of the blown air outlets it must either be raising the heater temperature which would cause overheat shutdown or it is escaping from the ducts.
A severe buildup of carbon can insulate the heat exchanger from the burning gases so much of the heat remains and is lost through the exhaust. In extreme cases the exhaust can glow.
If these are not the causes the heater is presumably not generating that amount of heat.
Burner may be damaged.

Unit fails after battery is connected or disconnected with controller switch on  -  Fault code 09
This fault code can often be caused by connecting the battery when the Eberspacher controller switch is on.
Sometimes it can be reset with appropriate equipment but not always.

Burner problems
Burners have a finite life and the mesh inside can eventually wear out.
Usual symptoms are black smoke and flame outs as the heater ramps up.
Recently we bought a used D4 burner cheaply from Ebay and cut it in half.
Now we can see why they fail and why burners cannot be cleaned by a simple mechanical clean. Click here for details.
We had one Eberspacher heater that we helped diagnose.
The unit ran ok but would intermittently flame out, sometimes completely but usually only for a second or so before re-igniting. The fault would occasionally not occur for 30 minutes but mostly happened within 5 minutes or less, sometimes about a minute apart. It sounded rougher than usual but had no flame outs. It also sounded unstable with the noise changing over a few seconds. I did at least 20 tests, starting from cold, warm and hot with two types of fuel but could not get any flameouts. The next day was cooler than the previous hot summer day, and I did a few more tests. It flamed out completely on the first test and shut down, when it restarted I could hear short blips as it flamed out and re-ignited. We were then able to swap components with our spare D2 and it turned out to be the burner. The burner looked perfectly clean but we cleaned it ourselves in a chemical cleaning solution. That gave no improvement. The heater was just on the edge of its failure point which is why we had difficulty getting it to fail on the first day.

Weird or intermittent faults
Sometimes the heater has faults that are confusing and don't seem to fit the normal categories.
These type of faults are not usually caused by ECU or component failure.
My first suspicion is usually power feed, either the battery or the battery supply wires both positive and negative and their connections. Flat batteries and low voltage are probably the major cause but are straightforward to diagnose and cure. See low voltage page. Leisure batteries deteriorate over time often without giving any warning signs, eliminate by substituting a known good battery.
Check for loose or corroded connections in all wiring not just the battery feed and return.
Check the brown/white earth wire, it can cause problems including erratic fan speed or odd controller behaviour.
Using the brown earth wire instead of the brown/white can also cause this.
Some battery chargers can cause problems, Ctek chargers connected with cables that are too thin are under suspicion.
Voltage spikes on the battery supply can be caused by other equipment, possibly high power devices switching on or off.
Fuel problems like bad fuel or air leaks, see fuel pages, can cause the heater to intermittently fail.
Occasionally a service can clear faults. This may be due to clearing bad connections during the procedure but in one case connections had been unplugged several times and before the service the heater still generated invalid fault codes greater than 100. The heater symptoms also included smoking and failures to start. The only reason I can think that the service solved the problem would be if the ECU itself was overheating. The blown air cools the ECU and it is possible a combination of coked heat exchanger, and too long outlet pipes caused this without tripping the overheat sensors on the heat exchanger. This is purely guesswork, it may or may not be true.

ECU / ICU fault.
The ECU ( Electronic Control Unit) controls all actions of the heater. In later models the name is changed to ICU (Integrated Control Unit). I refer to both of them as ECU on this website, rather than saying ECU / ICU. They are often described as the brains of the heater. ECU failures could cause the majority of the faults listed to occur so I usually do not mention it specifically in the diagnosis. There is no easy way to determine if the ECU is faulty except by fitting it into a working heater or replacing it with a known good one.
The majority of the ECU must be working to send the diagnostic information to the controller.
Diagnostic readouts can sometimes mislead as a damaged ECU can indicate components outside the ECU.
Older model ECUs have been repaired but I have only heard of one successfully repaired Airtronic ECU, they are also filled with a black material, replacing is the only option. We learn a lot from faulty components so if you replace one please donate your old one to us.
ECUs are extremely expensive, ebay may be the cheapest source.

Why do ECUs fail?
Reasons for ECU failures are given on the ECU Failure Reasons page.
Eberspacher say they are getting a higher ECU failure rate with heaters fitted on boats than on vehicles.
Factors external to the heater must be the cause otherwise vehicle heaters would suffer the same failures.

The following are not faults but might be thought to be.

The unit is noisy.
When the Eberspacher is switched on and it reaches maximum power there is jet like roar. It is not loud but could disturb adjacent campers or boaters, especially in quiet locations. The noise reduces as the heater power drops. Fitting an exhaust silencer does reduce the noise level and I consider one essential on mine.
The vehicle type silencer is not gas tight so should not be fitted inside boats, boat versions are longer, they are also more effective.
The combustion air inlet produces a low level noise, fitting a silencer reduces it further.
More details on silencers are on our Buying advice pages.
Silencers are also available to reduce the blown air noise, they are big.
If the heater has previously been turned on and left in standby by reducing the temperature setting it does not go to the highest setting when restarting so will be quieter.
The clicking of the pump can be reduced by fitting one of the newer rubber clamps in place of the older type clamp. (see Buying advice pages). Personally I like to hear the clicking as it tells me what heat setting the heater is using.
Metal fuel pipe can transmit this noise throughout the boat via the fixing clips. Fit the pipe inside cheap 6mm internal diameter hose and clip that.
Blower motor bearings can wear and become noisy, on some models they can be replaced.
An unusual cause of noise is pumped fuel volume too high, an Airtronic D2 pump fitted on a D1LCC caused a louder and much rougher burning noise and a whistling sound as well as overheating.

There is not enough heat.
If air ducting is long and passes through areas like lockers that do not need heating insulate the outside of the duct to reduce losses. Insulation similar to http://www.screwfix.com/p/thermawrap-loft-insulation-400mm-x-5m/76477 looks like it could be a good solution. Note the quoted figure equivalent to 55mm polystyrene will be very optimistic, some time ago I read information that this only applies if the insulation also trapped a fixed layer of air, I cant remember how much but it was inches.
We have met instances where people expect a heater like a D2 to heat a large boat. A D2 will only supply 2000 watts so may be too small, upgrade to a larger heater like a D4. All D4's are physically larger and the ducting has to carry twice as much heat so its diameter might need increasing.
Changing from fresh air supply to recirculated air is not the ideal solution for some users because of condensation but it could help in some cases.

Unit takes a long time to reach maximum heat.
The heater should reach its maximum heat output in under 5 minutes. If the air ducts are long and unlagged through cold areas they can absorb the heat increasing the time taken for maximum heat to reach the outlets.
See also previous item.

Page 1 contains most common fault details.
Faults during running.
The D2/D4 glow pin is ceramic and smaller than older versions.

How an Eberspacher D2 should start up when working properly without any faults.

D4 and D1LCC sequences are different and are listed at bottom of the page.
Stage 1 Switch on.
  When the D2 heater is switched on, the indicator light in the controller illuminates showing the heater is on.
  There may be a small click in the heater as the relay switches.
Stage 2 Pre start checks.
  Control unit does an electrical check of the glow pin, flame sensor, temperature sensor, fuel metering pump, control unit and possibly the fan. The fan may pulse once or turn slowly. These checks are completed in about 3 seconds.
Stage 3 Preheat.
  Glow pin is energized and starts preheating the combustion chamber.
  Blower turns slowly for about 40 seconds, then increases speed slightly.
Stage 4 Fuel on.
  At 60 second point pump starts, increasing pump speed for 5 seconds then drops immediately to medium pumping rate,  at same time fan speed increases gradually up to medium.
  White smoke which is the result of incomplete combustion of the diesel fuel may come from exhaust.
  The fuel air mixture flows around the glowpin and the hot glowpin screen.
  Once the fuel ignites white smoke stops and you hear a jet like noise which increases.
  When the flame detector detects the flame, in the manual this is shown occurring at the 80 seconds point which is possibly fairly typical, the glow pin will then remain on for a further 60 seconds (140 seconds point in the example).
      If the heater does not ignite within 90 seconds after starting the fuel pump another start attempt is made.
      If the heater still does not ignite after another 90 seconds of pumping fuel, the heater is switched off,
      i.e. the fuel supply is off and the fan runs on for about 4 minutes.
  At 100 second point fan speed and pump rate increase.
  At 260 second point the heater is at maximum fan speed, pump speed, fuel quantity and roaring noise.
  Once the heat exchanger reaches optimum temperature the Eberspacher switches into control mode, the pump rate and fan speed are controlled by the ECU to give the required heat output - Boost, High, Medium, Low or Standby.

When the heater is switched off, the fuel pump stops and the glow pin is switched on for 40 seconds to clean off any combustion residues. The fan speed gradually reduces, it continues to run for 4 minutes to cool the heater.
If the heater is restarted and the heat exchanger is too hot the fan will run to cool it before restarting.

Eberspacher D1LCC heater Normal start up sequence.

How the Eberspacher D1LCC heater should start if there is no fault and everything is working properly.
The manuals do not contain much detailed information on the start sequence.
Stage 1 Switch on.
   When the D1LCC heater is switched on, the indicator light in the control element illuminates showing the heater is on.
Stage 2 Pre start checks.
   Control unit does an electrical check, no details given of what components are checked, probably similar to D2.
Stage 3 Preheat.
   Glow pin is energized at 3 seconds point and starts preheating the combustion chamber.
   Fan starts at slow speed.
Stage 4 Fuel on.
   At 15 second point pump starts.
   White smoke which is unburnt fuel may come from exhaust.  Ignition will take place as the fuel air mixture contacts the glow pin.
   When heater "catches" smoke stops and you hear a jet like noise which increases.
   Once the flame detector detects the flame, the glow pin is switched off before 90 second point.
   No information given on when fan speed increases.
      However if the heater does not ignite within 90 seconds after starting the fuel pump the start is repeated.
      If the heater still does not ignite after another 90 seconds of pumping fuel, the heater is switched off,
      i.e. the fuel supply is off and the fan runs on for about 4 minutes.
   The heater is in the POWER stage with maximum fan speed, pump speed, fuel quantity and roaring noise.
Once the heat exchanger reaches optimum temperature the Eberspacher switches into control mode, the pump rate and fan speed are controlled by the ECU to give the required heat output - High, Medium, Low or Standby.

When the D1LCC heater is switched off, the fuel pump stops and the glow pin is switched on for 15 seconds to clean off any combustion residues. The fan speed gradually reduces, it continues to run for 3 minutes to cool the heater.
If the heater is restarted and the heat exchanger is too hot the fan will run to cool it before restarting.

A less likely reason is a faulty temperature control on/off switch or the wiring to it.
Once you have confirmed power into the Eberspacher is ok check for 12v on the red wire on the temperature controller. If it is absent and the loom contains two fuses check the 5A fuse, otherwise the wiring may be faulty.
With the heater switched on check for 12v on the yellow wire.
If it is not ok jump a short circuit across the red and yellow wires or join the two together.
If the Eberspacher starts operating the fault is the switch. Disconnect the yellow wire from the switch and then vigorously switch on and off a number of times, this can often clean the switch contacts.

When the heater is switched on, nothing happens except the controller light or display is on.
This condition is very similar to the pre start failure condition shown below so also check that section.
Check for a discharged battery, there can be enough power for the light but not for everything else to work.
If the loom is the version containing two fuses check the 20 amp fuse.
With the controller switched on check for +12v on the yellow wire, or on Pin 4 on the back of the D2/D4 connector.
  If absent jump a short circuit across the red and yellow wires or join the two together, the controller can still be connected. If the heater starts the fault is the controller.
Disconnect the Eberspacher D2/D4 connector, check for corrosion on the terminals.
The heater might be locked out after overheating, fault codes 15, 17, 50. Some D1LCC heaters versions can lock out after 5 identical faults, details on Simple faults page.We have not encountered this.
Providing no other components are damaged the ECU can be reset with equipment like the diagnostic unit, 7 day timer, 701, 801 or EasyStart Select controllers.
Check ECU, more info in ECU faults section.

When turned on, the heater just blows cold air, never stops and does not perform a start attempt.
Check if the Ventilation button was pressed instead of Heat by mistake.
Check controller, a fault could result in it switching to ventilation mode instead of heating mode.
  The Operator control unit set value potentiometer section below gives details on diagnosing the controller
Check the flame and overheat sensors as described below, a sensor can falsely indicate the burner is hot and requires cooling.
  A bad or loose connection of the sensor plug could cause this.
Check target temperature grey/red wire for a short circuit to earth or to brown/white or brown wires.
   Make a visual inspection for bare wires and anything touching.
   Disconnect heater and controller, then test grey/red wire for short circuits.
      Use the multi-meter, set it on the ohms range as in the overheat sensor test below.
      The meter should give an out of range indication ( 1    . ) for no short, 00.0 for a fault.
Check ECU. Unfortunately this seems to be one major ECU failure symptom for Eberspacher Airtronic heaters.

Fuse blows when connected or when switched on.
If the battery has been removed check it has not been re-connected the wrong way round by mistake.
    Check this before replacing the fuse, if the ECU has a protection diode it may have blown the first time it blew the fuse.
    It may not protect a second time, (just hope it managed to protect the first time!).
Unplug the Airtronic heater connector and replace the fuse, if it is ok the loom wiring is ok
   Remove the fuse before reconnecting to prevent sparking causing damage to the contacts, then replace the fuse.
The ECU checks the Glowpin, Blower, Pump(s), Controller, Flame sensor and Overheat sensor during pre startup checks.
   It aborts if any of these are short circuit so these should not be the cause of blown fuses.
If the 20 amp fuse is blowing on Airtronics heaters unplug the four 2 pin connectors from the ECU as a double check and try again.
   If the fuse still blows the ECU is faulty.
If the 5 amp fuse is blowing on Airtronic heaters check the controller and its wiring.
On other heater models it is more difficult to isolate parts, unplug the ECU and check everything else for short circuits.

Stage 2 Pre start check failure.
The heater turns blower a few times, pump and ECUs relay may click one time but heater will not make an attempt to start.
Check for bad power connections or a discharged battery.
A fault in any component in the list below prevents the startup continuing.
The test limits during startup are set quite wide so when checking you need only check for components that measure very different from normal.
Ensure the item is disconnected from the Electronic Control Unit (ECU) before making any measurements.
Measure the electrical resistance of each item for short circuit or open circuit components, faulty wiring, check for unplugged connectors.
Some older models do not automatically reset after overheating, they have a reset switch on the top of the heater under a rubber bung.

Checking for power on the D2/D4 connector.
For those unfamiliar with multimeters it is set to 20v dc range.
Battery voltage will usually be between 11 and 15 volts.
If the probes positions shown here were swapped it would read -12.37
If there was no voltage it would read 0.00

Note this test should not be used to check for low voltage as the Eberspacher needs to be connected and running during startup for low voltage testing.
These timings from our own heaters may help while confirming 'two start attempt failure' symptoms.

Test of glow pin giving a reading of 1.1 ohms.
The meter reading has increased by 0.5 ohms
which is the resistance of the glow pin.

Multimeter leads connected together.
Meter is set to lowest range, 200Ω.
Resistance value of leads 0.6 ohms.

Flame sensor    Fault codes 064, 065,  also 013, 014, 051.
   Disconnect the green connector from the ECU and measure the flame sensor resistance across the green and brown/white wires.
   It should be approximately 1000 ohms at room temperature. (1000 is also referred to as 1k or 1k0)
   At 20 deg C quoted value is between 1056 and 1100, at 0 deg C between 980 and 1020 ohms.*
   Check the green connector is not corroded and is fully pushed home.

Overheat temperature sensor    Fault codes 071, 072,  also 012, 014, 017.
   Disconnect the green and blue connectors from the ECU and measure the sensor resistance across the blue and brown/white wires.
   It should be approximately 60,000 ohms at room temperature. ( 60,000 is also referred to as 60k)
   At 20 deg C quoted value is between 59.3k and 65.8k, at 0 deg C between 155k and 175k ohms.*
   Check both connectors are not corroded and are fully pushed home.

*In practice the Eberspacher does not know the actual temperature and start up check limits will be very wide.

Airtronic Combined Flame and Overheat sensor.

Airtronic Flame sensor test.
Meter set on 20kΩ range.

Airtronic Overheat sensor test.
Meter is set on 200kΩ range.
Difficult to hold probes onto connector contacts,
nearly impossible with other hand holding camera.

Fuel metering pump    Fault codes 047, 048,  049
    Check the wiring connections are tight and free from corrosion on the pump terminals and at the end of the wiring loom.
    Check the Airtronic type fuel pump connector has correctly locked into position, photos below.
    Check the wiring between these two points for damage.
    Disconnect the pump either at the pump terminals or at the end of the loom.
    Measure the resistance of the pump which for 12v should be between 9.0 and 10.0 ohms  (24v between 34.2 and 37.8 ohm).  In practice the check limits are set wide, a 24v pump on a 12v Ebespacher, ie about 3 times the resistance, passed Eberspacher electrical fault checks, only failing on pumping fuel.
    Alternatively test the pump, details on the fuel page.
    Many users assume the pump is faulty because it is not pumping, note that it will only pump once all pre-start checks are passed.
    Some ECU faults can apply continuous power to the pump causing it to get hot during these checks.
Heater Model
Switch on
Pump start try 1
Pump stop try 1
Pump start try 2
Pump stop try 2
Fan stop

Airtronic D2
Airtronic D4
Heater makes two attempts to start, then stops. During both attempts it sounds as if the heater started before it stopped. Usually there is only a short burst of smoke as when the heater starts normally.
   The heater ignited but the flame was not detected. Check the flame sensor.

Heater starts with difficulty, often on the second attempt with a lot of smoke.
   Fuel has degraded or contains water. See Fuel page and Fuel problem pages.
   Check the fuel filter, do a fuel volume test.
   The Eberspacher requires servicing, this was the reason we serviced the D2 shown in detail on our Service page.
   Dereks tip - It may be worth trying running on a can of Kerosene (central heating oil) or paraffin.
                    This can burn off some of the deposits increasing time before a service is needed.
   Eberspacher recommend servicing each year, more often for some fuels, or every 2 years for low usage heaters.
   Check exhaust pipe and exhaust silencer for blockages.

Heater emits a smoke screen when started after servicing.

Stage 3 Preheat failure.
Heater switches off at any time before completing start sequence.
Flat battery or a bad electrical connection, usually the fan does not run on for cooldown period.
Heater switches off after about 10 seconds     Fault code 33.
The fan is checked when it is rotating about 10 seconds after switch on.
A magnet mounted in the impeller is detected by a sensor inside the ECU as the fan rotates.
  Check the ECU is correctly mounted and the magnet, shown above, is in place.
Heater switches off before completing start sequence, typically after 20 to 45 seconds.   Fault code 11.
While the glow pin is energised the Eberspacher takes maximum battery current, (8 Amps for D2 & D4, 20 Amps for older models.)
   If the voltage at the heater terminals drops too low for 20 seconds the heater is switched off,
   usually switching off between the 20 and 45 second point.
   The voltage at the heater can be a lot lower than the battery terminal voltage due to losses in the wiring.
   This is a very common cause of failure and is covered in detail in the Low Voltage page.
Heater switches off before completing start sequence.
The speed of the blower motor is monitored continuously. If the fan motor does not start up or its speed deviates by more than 10% the heater is switched off after 30 seconds.
Heater goes through normal start sequence but pump does not pulse, usually when first used after summer.
Pump may have seized mechanically. See fuel page for solutions.

Stage 4 Start failure.
Heater makes two attempts to start with no success and then stops completely, no smoke comes from the exhaust pipe or heater makes two attempts to start, may smoke for a while or smoke heavily and then it stops.   Fault codes 52.
Eberspacher recommend  servicing the heater annually so this would usually be our first step if the heater is producing smoke, especially if one had not been done recently, (see servicing pages for DIY servicing details).
White smoke is usually heated fuel and air mixture that has not been burnt, no smoke may mean no fuel is reaching the Eberspacher.
   Check if you have run out of or are simply low on fuel, a tank pick up tube can be 50mm or more above the tank bottom. This ensures there will be enough fuel left to run the engine and prevents water and crud in the bottom of the tank from being picked up.  As an example on one camper van the tank holds diesel for about 250 miles but the heater stops working after 200 miles.
   If the fuel pipes were empty before starting check if purging of air is complete.
   Check fuel is arriving at the heater, disconnect fuel pipe, fuel should squirt out on each pump stroke.
      If there is no fuel look at the Fuel Supply Faults page.
   Do the fuel quantity check, if the amount of fuel is insufficient -
      Check the fuel lines and connections, fuel filter for air leaks and blockages. Check all clips are tight.
      Check the fuel pick-up pipe, on some non Eberspacher types the tube pushes into the upper part and can have an air leak.
      Check condition of rubber sleeves, they swell and can become porous as they deteriorate.
      Check pipes butt together inside the sleeves, gaps can trap air bubbles.
      Check pump has not been knocked or the fixing bolt become loose so pump is at an angle of less than 15 degrees. (see Fuel page)
   Check for water in tank, water from condensation builds up in bottom of tank and it can be pumped instead of fuel.
   Check if exhaust pipe / silencer or combustion air intake pipes are blocked, possibly with ice or water.
   If a service is not done check the glow pin, clean ventilation hole above the screen in the glow pin chamber.
   If the screen is removed check the fuel inlet hole is clear. It may also be worth blowing through the metal fuel pipe section from where the fuel pipe is connected to the glowpin chamber, it possibly may need an air compressor or a bicycle pump, before fitting the new screen.
   Check fuel for degradation and floating debris, see fuel page.
   Check also the Eberspacher starts normally but stops whilst running, it may try to restart category as causes can be the same.

Blower motor connector.

Eberspacher heater smokes excessively during starting.
A modern heater in good condition may produce a slight amount of smoke for a couple of seconds whilst starting. If carbon is allowed to build up, the fuel takes longer to ignite so startup smoke intensity and duration increases, our spare D2 which had not been serviced since we bought it smoked for about 4 seconds. Some unburnt fuel smell is normal during startup. Usually once the heater temperature rises there will be no visible smoke. Condensation from the hot gasses will be more visible in cold weather so make allowances for it.
White smoke for more than a few seconds at startup is a symptom of incomplete combustion or a weak air-fuel mixture.
  Servicing the heater usually cures the problem, it is covered in detail on our Service pages.
  Check for fuel problems, do a fuel quantity test.  Check motor speed.  Check for blocked air inlet and exhaust pipes / silencer.
White smoke / steam as the exhaust heats up may also be from water / condensation in the exhaust.
  Note combustion gasses always contain a considerable amount of water vapour.
  Reroute exhaust so it runs downhill or fit a drain fitting. They are listed in the Eberspacher Marine installation manuals.
  Reposition exhaust outlet or fit higher above the water line.
Black smoke means a rich fuel air mixture, wasted fuel and more carbon build up. A rich mixture can also cause overheating shutdowns.
  Service heater. Check for blocked air inlet / exhaust pipes / silencer.
  Check for fuel problems, do a fuel quantity test. Check motor speed.
  Burners will eventually wear out but the symptoms are unlikely to occur quickly, they probably develop over several months.
Some very old heaters have simple controllers which do not delay pumping the fuel until the glowpin has heated up so these can smoke quite badly during startup unless everything is really clean.
Check the items in the following fault.

Eberspacher heater carbons up regularly requiring frequent servicing.
In general Eberspachers like to be worked hard. Prolonged running on the low heat setting with some fuels can cause carbon build up. This can be reduced by regularly running the heater at maximum heat output for about half an hour.
Another reason is the choice of fuel; biodiesel and gas oil carbon up the heater far quicker than white diesel or kerosene.
Derek's D2 was smoking and ready for a service when he changed to 28 second Domestic heating oil (standard kerosene). The smoking cleared and it has run for about 5000 hours mostly on low without any sign of needing a service. He thoroughly recommends this fuel.
Check the fuel pump is not less than 15 degrees from horizontal.
Perform a fuel quantity check, it only needs to be slightly outside limits to affect the burn.
Check for blockages in the combustion air and exhaust pipes / silencer which obstruct the gas flow.
On boats check fenders are not blocking combustion air or exhaust.
Check the combustion air and exhaust pipes are between 0.2 and 2m long, they do not have to be the same length on a D2 or D4.
Check exhaust gasses are not entering the combustion air inlet.
The maximum combustion air temperature is 25 degrees C, this can be exceeded in some engine compartments, draw air from outside.
Check motor speed. Check gap between combustion air blower and body is 0.3mm with a feeler gauge, this is same for all heaters.
Check for degraded fuel.
If the glowpin screen has not been replaced during the service it may be clogged.
Bigger is usually not better, fitting an oversized heater is not good, it will run on lowest setting or standby most of the time.
Water heaters can suffer badly from carboning up and Eberspacher did investigations and found several reasons and solutions which are covered in a Technical Bulletin  It also applies to other boat installations, click here to view..

The heater set temperature control seems to have very little relationship to the ambient temperature.
The set temperature controller does not have a temperature sensor inside, all it does is to ask the Eberspacher to set its output for the temperature set on the controller. The heat sensor is located inside the Eberspacher in the inlet for the heated air.
This arrangement works ok in a small vehicle cab but is not very good when the Eberspacher is situated far from from the heated area.
It fails completely when the heater is fed from fresh air. The sensor then thinks that the temperature of the outside air is the ambient temperature and of course that does not change as the heated area warms up. Even worse if the outside temperature drops below about + 10C the heater automatically switches to maximum heat output, completely ignoring the temperature controller setting.
The solution can be to fit a remote temperature sensor. For details and how to get a sensor cheap see the sensor page.
The 801 controller has a remote sensor inside but it may still be worth fitting a separate sensor so it can be positioned in a different position to the controller.
See also the next categories.

The heater stays in full power mode.
Is it just too cold? Derek's heaters will not drop to low power if the temperature of the returned air is fairly low even with the controller set to minimum.
See the previous category for heaters drawing fresh air from outside.
If a remote sensor is already fitted it may have failed or its connecting wiring (grey and brown/white wires) may be broken or have bad connections.
Controller faulty.
ECU faulty, we know of at least 2 with this failure symptom.

The heater drops down to low heat prematurely.
If a remote sensor is fitted has something that generates heat been placed below it or near it.
Another likely cause is the returned air being drawn from close to the Eberspacher, ie no inlet air ducting.
The air surrounding the Eberspacher can get hot from the heat passing through the case and the heated air ducting.
If the heater is in a space that is not well ventilated that air temperature can easily be 30 degrees C or higher.
The manual quotes a maximum allowable air inlet temperature of 40 degrees C.
When that air is drawn into the heater the temperature sensor inside the air inlet senses the heat and turns down the heating.
Add a returned air duct and / or improve ventilation around the Eberspacher.
A remote sensor may help.
Check length / number of bends etc of heating ducting is within specification as in the 'Eberspacher starts normally but stops whilst running. It does not try to restart' section. Derek experienced a problem of reducing heat on his D4 which was hooked up to some existing ducting with too many bends.
Check controller.

When the heater switches into standby there is a large temperature drop before it will restart.
This is normal. Eberspacher temperature regulation is not brilliant. They have 4 (less for some models) heat output settings and some tweaking of the control is often required.
According to Eberspacher, Airtronic heaters will maintain a temperature within approximately 4C (7F) of the desired heat comfort level by regulating between Power, High, Medium or Low heat output. Should the temperature rise above the desired heat comfort level by 2C or more, it will then switch off into standby until the air temperature drops down by approximately 4C.
Assuming the 4C quoted is from the switch off and not from the comfort level temperature the temperature can change by 4C from when the heater switches off to when the heater is restarted.
I am more familiar with temperatures in Fahrenheit, if it switches off at 70F it might be 63F before it restarts, distinctly chilly!
This poor temperature control will not be changed by fitting a remote sensor or an alternative controller.
Derek's tip for his Airtronic D2: If you feel cold when heater is in standby just tweak the control higher for a couple of seconds then return it to original setting, that usually restarts it.
Duncan Grey has suggested another way to deduce the difference.
He positioned his remote sensor closer to the heater output so it received some direct heat, making it hotter than the general air temperature. When the heater goes into standby it cools down faster. The temperature setting on the controller has to be set higher but net result is less temperature difference.
Downside of reducing the hysteresis is shorter running time per cycle and more starts. This probably will increase the need for servicing and make more noise as starts are noisier than normal running.
My alternative suggestion is to fit a Y piece with an adjustable flap, available on ebay, one side for heating output, the other diverting some of the heat outside.
That way the heating supplied to the cabin can be reduced to a level that keeps the heater running continuously on low setting so it does not switch off. Sounds wasteful but a D2 only uses 0.1L of fuel per hour on lowest setting and you should get a reasonably constant temperature.

The blower motor is monitored continuously during operation.
Shut down will occur if the blower does not start or its speed varies from specification by more then 10% for longer than 30 seconds.
If available use a non contact RPM meter to measure speed of blower, otherwise check for obviously wrong speeds.
I bought a non contact laser tachometer / rpm meter on ebay for 8 including post December 2012.
Quoted speeds are from the manuals but treat these with caution as Eberspacher may change the speeds in later production runs.
  D2  Power 4800 140 rpm, Fast 4000 120 rpm, Medium 2800 80 rpm, Slow 2000 60 rpm
  D4  Power 4400 130 rpm, Fast 3500 100 rpm, Medium 2600 80 rpm, Slow 1600 50 rpm, Standby measured about 600 rpm.
  D5  Speeds not quoted in manual
  D1LCC  Power  5000 rpm, Fast 4400 rpm,  Medium 3000 rpm   Slow 3000 rpm
  D3LCC  Power  4200 rpm, Fast 4200 rpm,  Medium 2200 rpm   Slow 3000 rpm  (Medium speed suspect, possibly error in manual?)
If RPM is too high, Airtronic, check magnet in impeller, photo Airtronic service page 2. The magnet detector is in the ECU.
If RPM is too low, check for air restrictions or blockage. Check fan is not catching on case or ECU.
Wiring to combined sensor sometimes prevents ECU locating far enough away from fan during fitting, move wires and refit ECU.
Check wiring for short circuit.
Worn bearings and brushes are generally the main reason for motor failures. See Blower page for repairs.
Do not connect the motor to 12v battery to test.
If the blower speed is erratic see also the Weird faults section.
Non contact RPM meter from ebay.
Kit contains a length of adhesive reflective strip for Eberspacher models which do not have a white stripe.
Does not work in bright sunlight but is ok with overcast daylight.

Point the laser from the side onto the white stripe on the air intake impeller to get a measurement of rotation rate.

Heater starts normally but stops whilst running. It does not try to restart.   Fault codes 012, 015, 017
The Eberspacher has overheated.
Overheat shut down can occur if there is a restriction of either the heating or the combustion air flows.
Often it is caused by bags or luggage blocking hot air outlets, results can be minor or extremely expensive.
If the blockage is minor (Fault code 12) it can be reset by switching off and then back on again.
More serious blockages or repeated faults can cause the ECU to lock up. (Fault codes 015, 017). The ECU can be unlocked with appropriate equipment. Complete blockages can cause the ECU to be damaged.
Tip: Check to see if the heated air outlet(s) could be accidentally blocked. If you cannot guarantee they will always be clear fit a protective cage or split the duct to feed multiple outlets so one is always clear.
Check for an obstructed heating air inlet or outlet or for crushed / melted air ducting hose (pictures below).
Check combustion air inlet, it draws air from the exterior so can sometimes be blocked by rubbish such as pieces of plastic debris.
Air inlet silencers may contain foam which can deteriorate and cause blockages, see the buying pages for details.
Check for blockages of exhaust pipes and silencer, carbon build up or exhaust sealant are common causes.
Is the heating air inlet clogged with fluff?. Are all, or to many, heating outlets adjusted to the no or low airflow condition?
Measure resistance of both the overheat sensor and flame sensor as detailed in the Stage 2 tests.
Check the overheat and flame sensor plugs and sockets for dirt or corrosion.
Check motor speed.
Is the Eberspacher clogged with carbon and in need of a service?, servicing details are on our Service section.
Is the pumped fuel volume too high?, do a fuel quantity test as detailed in the Fuel Problems page
If you have altered the heating air ducting check length / number of fittings etc is within specification, detailed ducting instructions are in the Marine Heater Installation Guide - Airtronic D2 D4 D5.
Note changing from a straight outlet hood to a right angled one can reduce the ducting allowance by up to 50%.
Poor ventilation around the heater is another possibility.
The overheat sensor is clamped to the outside of the heat exchanger casing at the top of the heater. Various temperatures  have been mentioned, we have heard it triggers at about 120 deg C for a D2 and 150 deg C for a D4 but cannot be sure. The actual setting is determined by the ECU software and can vary under specific conditions.
The sensor returns to normal when the heater cools down.
Once the problem is removed, the heater can often be re-started by switching the heater off then back on.
Overheats are potentially dangerous and can damage the ECU so don't just keep resetting without finding the cause.
Blocked outlets have damaged several of our readers ECUs, see above to prevent this.
We know of one Eberspacher where changes to the ducting damaged the ECU and melted the plastic combustion air impeller.
Another user crushed the case which jammed the impeller and the overheat damaged his sensor, photos on the Autopsy page.
Some heaters will be locked out if there are too many overheats, cure fault before resetting with appropriate equipment

Airtronic D2 D4 and D5 heaters will lock out in extreme overheat conditions.
This is my best guess as to why the overheat sensor sometimes fails to stop this happening.
If the heating airflow is partially blocked there will still be some transfer of heat to the airflow, temperatures inside the heat exchanger will build up relatively slowly and the overheat sensor will shut off the heater with fault code 12, the fan will then continue running allowing some cooling after fuel is stopped.
However if the heating airflow is almost completely blocked there will be very little heat transferred by the airflow.
It takes time for the heat to transfer through the casing of the heat exchanger and the base of the overheat sensor so there will be a delay in detecting the overheating. Once the sensor does reach the normal overheat temperature limit the ECU shuts down the heater.
During that delay the heater continues burning fuel and much more heat is transferred to the heat exchanger inner surfaces.  That heat then flows through the heat exchanger to the outside of the casing and without sufficient cooling airflow the temperature rises rapidly until the overheat sensor is too hot for the system to measure.
At that point the ECU is locked as a safety precaution to prevent the heater being restarted .
A diagnostic readout would then give three fault codes, 12 Overheat, followed by 17 and 15  Excessive overheating.
If there is no airflow the heat exchanger outside temperature can continue to climb above the lock out limit.
While all this is happening some of the heat transfers to the ECU and if its temperature becomes too high components inside can fail.
Once the heater has cooled down the ECU can be reset with appropriate equipment provided it is not damaged
Another reason for these codes could be an intermittent fault on the overheat sensor.
A D1LCc will lock out the ECU after 3 successive overheat faults
Lockouts can be reset with diagnostic equipment like 701 or 801 controllers.

Melted hose caused by a break in the inner core allowing hot air into contact with the plastic outer covering.

The inner hose fell apart during removal.
Before doing any tests ensure the battery is well charged and in good condition.
Leisure batteries often are not regularly replaced and can deteriorate badly without users realising.
This causes many problems, the easiest way to eliminate is by substituting  a known good battery.
Battery chargers can cause or conceal problems so usually disconnect them during tests. 
Check all electrical connections for corrosion.
The purpose of this site is to promote our Le Tonkinois varnish and Flexidisc products.
Please look at those products as a thank you for this free Eberspacher advice.

Close up view of the ECU holding clips.
Also shows the magnet mounted in the impeller.

The Eberspacher ignites normally, drops back and switches off into stand-by mode, blower is slowly spinning but the heater never restarts.   No fault code.
The heater thinks the air temperature is higher than the temperature control setting. Is the temperature control set too low?
If not temporarily replace the temperature control with a 2200 ohm resistor as described in Stage 2, this simulates a high heat setting.
If the control is not faulty the temperature sensor in the ECU might have failed. In practice this is not something we have encountered and it is impossible to diagnose without installing an external temperature sensor.
The blower on Airtronic heaters fitted with a remote sensor will be stationary in stand-by mode, not slowly spinning. I do not know if it is the same on any other models.
If a remote sensor is already fitted is it receiving heat from somewhere, like hot pipes behind the panel or something hot below it?
This is also an ECU failure symptom.

Eberspacher starts normally but stops whilst running, it may try to restart.     Fault codes 053, 054, 055, 056
The Eberspacher has flamed out. If the air / fuel mixture proportions change too much the flame will extinguish and the flame-out causes the heater to shut down.
The most common reasons are no fuel, bad pipe connections, blocked fuel filter, blocked or kinked pipe, air leaks or an air lock.
Rubber connectors deteriorate. They swell constricting the flow, often become porous, bits and flaps of rubber can cause blockages. They can also fail to reseal after disconnection. They should be renewed periodically.

Checking the blower motor combustion impeller clearance with a 0.3 mm feeler gauge. The gap is the same on all Eberspacher heaters except Hydronic 16-35kw models.

Fault lock out
    Starting failures are more likely to be caused by the above faults so eliminate these causes first.
    The ECU can be locked after a serious fault condition, usually bad overheating.   Fault codes 015,017,050,099.
    It is locked for a good safety reason to protect both you and the heater.
    DO NOT RESET until the cause has been cleared.
    Depending upon the overheat severity other components may be damaged.
    Personally I would dismantle the heater to check items like the fan impellor for damage.
    While it is apart it would be sensible to do a full service as the same time.
    The lock out is reset by clearing the fault codes with diagnostic equipment such as the 801, 701(blue logo) and EasyStart controllers.

You use any information and advice we give entirely at your own risk.
If you do not accept this do not use this site, go to an Eberspacher dealer.
We have tried to make it as accurate as we can but accept no liability for errors or problems caused by following our pages.
Some of the information is only suitable for people with a good aptitude for mechanical and electrical repairs.
Any DIY involves some risk of accidents and you must decide if you are capable and can do it safely before carrying out any work.
You should also ensure your DIY is done to a professional standard in order to avoid creating potential hazards and insurance invalidation. Boat installations must strictly comply with Marine regulations.
When ambient temperatures are low heater starts with difficulty or fails to start.
   Fuel is unsuitable type or has degraded. See fuel pages and Fuel problem page.
   Battery in bad condition or discharged, see low voltage page for solutions.

Eberspacher needs to have engine running or be on shore power to start reliably.
   Classic symptoms of low voltage problems, see low voltage page for solutions.

Eberspacher clearing a large amount of unburnt fuel.

It's not only Eberspachers, Video of a smoking Webasto.

When Eberspacher heaters fail the smoke can be alarming and it may look like the heater has blown up and needs an expensive repair.
In reality this is usually easy to fix as the smoke is generally unburnt fuel, and a service can fix the problem.
One point that can easily catch users out is after repair the heater may still emit clouds of smoke even though it has started ok. We did an unnecessary stripdown on one of our heaters when this happened.
When the heater fails to start fuel is pumped until the heater aborts the start attempt, it then retries a second start.
The user then turns the heater off and tries again, usually for several times in the vain hope it will start.
The unburnt fuel builds up and has to go somewhere, some will be vented out the exhaust as smoke, the rest pools in the burner, exhaust pipe and silencer.
After repair the heater fires up ok, the exhaust gasses are not hot enough to ignite the unburnt fuel but vaporise it and it comes out the exhaust as smoke. Sometimes this is even more spectacular than the original fault!
Once all the unburnt fuel has cleared the smoke should stop.

Water in the fuel collects at the bottom of the tank and too much obviously prevents combustion. Smaller amounts sloshing about can be picked up and cause intermittent flame failure.
Wrong pump or the pump at an angle of less than 15 degrees can deliver the wrong amount of fuel. (more info on fuel page)
Unsuitable or degraded fuel can cause flame-outs at low temperature particularly at the lowest heat setting.
Flame-outs may be caused by a clogged glowpin screen, blocked breather hole, blockages inside the burner, heavy carbon deposits as well as blockages in the combustion air flow or exhaust system including the silencer.
Cleaning a burner mechanically during a service will not remove deposits inside the inaccessible parts, a chemical clean may be required.
Also check the Start failure category as causes can be the same.
More causes and details in the Fuel Problem and Servicing pages.
If a flame out happens after the heater has started, the heater will attempt one restart.
If another flame outs occurs within 10 minutes the heater will not restart.
Low battery voltage can also stop the heater, full details are on the Low voltage page.
The following are not common but if all the above have been eliminated they may be worth investigating:
   The combustion impeller to blower body gap is 0.3 mm and is critical for how much air is pumped.
     Check using a feeler gauge at several points in case the fan is distorted or bent.
     The combustion impeller is pressed onto the splined shaft on D2 & D4 models so can be adjusted.
   The fuel pump may be intermittent. One pump had dirt on the ball bearing valve seat, it passed a fuel quantity test ok.
   Burners have a finite life and can eventually fail. Unlikely to develop suddenly, usually will develop slowly over several months / years.
     No way of diagnosing burner failure, eliminate all other causes first. Then usually eliminate by substituting a known good burner.

This flap partially blocked the rubber fuel pipe.
Flaps are usually caused by inserting a fuel pipe with a sharp edge.

Photo Matt Dimmick

Operator control unit set value potentiometer, sometimes called the rheostat or set temperature control.  Fault codes 62, 63.
    The control can be substituted by a simple diy controller for testing, details on the controller page.
       Connect the potentiometer to the grey/red and brown/white wires instead of the control.
    Then start the heater, either with the control switch or by joining the red and yellow wires.
    Check grey/red and brown/white wires to the control for a break or short circuit.
    An alternative testing method will only work for a rheostat, it will not work with more modern controllers.
      Disconnect the grey/red wire from the terminal on the controller.
      Measure resistance from the terminal to the brown/white wire, the control should adjust from 1750 to 2180 80 ohms.

Blower motor   Fault codes 031, 032, 033, 034
   As the fan is pulsed during this period it is likely it is checked for electrical resistance.
   If the other components are ok and the fan does not pulse once or turn slowly check it is free to rotate.
     The fan blades can catch on the case or on the ECU.
     The glowpin wiring can cause the ECU to be positioned incorrectly.
   Check the resistance of the motor is roughly 0.5 ohms.
   For repair of blower motors see Blowers page.
Airtronic type fuel connector.
Metal spring in locked position, Left.
Push in & release position, Right.

If connector is fitted without depressing spring it is prevented from pushing fully home and does not make a connection, a fairly common fault.