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1    Eberspacher Airtronic ECU dismantle for Technicians (not DIYers).
If repairing an Airtronic ECU was reasonably straightforward someone would be offering a repair service, no-one does that. To date I have heard of only one successful repair to an Airtronic ECU and that was for a fault that is rare. The chances of a non specialist DIY repairer succeeding is extremely unlikely. Additionally working on a printed circuit with SMD devices needs expertise and often specialised soldering equipment. Why then do I include a page showing how it comes apart?
I guess every electronics technician / enthusiast has at sometime been presented with a faulty bit of equipment by a friend with the comment "You know about electrics, can you have a look at this for me?". You then waste a couple of hours working out how it comes apart before finding it is not feasible to repair. The page shows what I found during my first disassembly attempt and what to expect once it comes apart. The ECU was not expected to be repairable so I was not worried about its destruction during disassembly. I would expect this page to be of help to technicians like TV servicing engineers who are used to working at component level. You will probably have far more servicing experience than I have. I am used to older generation equipment that can be taken apart with a screwdriver and with components that are big enough to see without a magnifying glass!  It should help to make a quick decision on whether it is worth even opening up the ECU and to work out the best way of disassembling it. Please feed back any hints, especially on freeing the pcb from the case.
This is NOT intended for DIY repairs.





Older type Airtronic ECU with plastic covered cable - Top.
Newer Hella Airtronic ECU with fabric covered cable - Bottom.
Some ECUs are yellow, it possibly may mean 24v version.
Older Airtronic ECU on left, newer Hella type on right.
The blue wiring is for the internal temperature sensor.
Newer Hella Airtronic ECU.
Details of how it came apart are not available.
The relay marking shows this is the 24v version. 12v version should only have minor physical differences but the ECU Eprom may hold different values for components checks.
ECUs are complex devices and this page is aimed at technicians / electronics engineers. ECU repairs are not suitable for unskilled users and I cannot give advice on fixing them. If you need to ask if changing a particular component will cure the problem it probably won't.
I welcome donations of faulty ECUs for all heater models, they allow further investigations into fault finding.
Older type Airtronic ECU.
This ECU was not thought to be repairable so no particular care was taken to prevent further damage during disassembly. It was dismantled just to find methods for taking apart and to see what components were used to get clues as to how the ECUs work.
Tip - Heat the metal cover with a blowtorch before removing.
Under the cover is this black material covering the pcb. That came away without too much difficulty giving access to the top of the double sided pcb.
After disassembly I found the pcb is held in the case by:
8 pins for fan, glow pin, flame & overheat sensors.(Yellow)
12 wires in main connecting cable. (Green)
3 pins hall effect fan speed sensor. (Cyan)
Black material between the pcb and case.
New type Airtronic ECU.
The neat arrangement of wires makes this look like a connector but it is a moulding to retain the wiring. The wires go direct to the pcb with no slack inside.
The moulding material was stuck to the wires, case both outer and inner as well as the pcb. Different from the black stuff under the metal cap and much more difficult to release anything. I dug out a lot of the material trying to free the wires. If the case is cut to help free the wires be very careful as the top of the CD4051BCM ic must be extremely close.
Having seen the freed connector pins on the Hella ECU  I tried freeing them by levering on the pcb and used far more force than I would dare to use if this was a real repair but nothing shifted. Finally these two pins pulled through the solder joint. Next time I would try heating the plastic before levering to see if that works. Alternatively you may be able to unsolder the pins ok, my desolder wick was corroded and only after I bought a new solder sucker did I realise just how much the spring on the very old one had weakened over decades.
After trying to free the pins by desoldering and not knowing what else was holding the pcb I sawed off two sides of the case, not something I would want to do for a proper repair.
Black material under the pcb starting to be separated from the case on this side.
The 3 pins of the hall effect fan speed sensor (mounted in slot front to the left of center) show the sensor had been pulled upwards and it looked like it would pull out ok. I then found it has been mounted from outside the case through 3 holes so will not come out any further. This needs to be unsoldered early before levering the pcb. Its position may be critical so note its position before starting.
Eventually I cut the case, leaving the connector pins section on the pcb and with a bit more levering the pcb came free.
Removing the black stuff was more difficult than that under the metal cover.
The bottom layer of the pcb revealed.
Another view.
Eberspacher ECU dismantle.
Click on images for a larger photo.


ECUs are made by two manufacturers, both come in 12 and 24v versions.
2    Eberspacher D1LC Compact (D1LCC) ECU.
Hella D1LCC ECU.
This circuit board layout is different to previous photo.
3    Eberspacher D1L ECU.
Remove the tape and bend back the case indentations, the ECU will then slide out of the case.
Resistor in front of pink capacitor has burnt and broken.
This resistor is clearly shown in the previous photo.
Resistor colour code     Green Blue Gold    Silver
5.6 ohm 10%, often written as 5R6  
Value is the same for both 12 and 24v versions.
I found this on a forum with the poster having the same problem and asking unsuccessfully for the component value so this may possibly be a common problem. In this case the capacitor is also damaged.