Replacing BECM power board?

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Henrik97

Active Member
Posts
301
Hi all,
As some of you may know, I attempted to repair my BECM after it had been subjected to moisture and fried a relay and a couple of pcb traces. I won't bore you with the full story again, so I'll stick to the issues at hand. The car is now working fine, with no excessive battery drain and no flickering lights, but there are some things that don't work as they should:

1. Power windows:
I used to have three out of four working, but this has now been reduced to only one (luckily it's the driver's front :)). I have inspected and tested the switch panel, and all the buttons do what they're supposed to. By this I mean that they short out the designated traces on the pcb, whereby grounding the respective pins on the control chip. I get the "not set" message when I push "up" on either of the malfunctioning buttons, but no message when I push "down". Locks, mirrors and sunroof are fine.

2. Cruise control: Hasn't worked since I got the car, and it still doesn't.

3. Heated seats:
I'm not sure the driver's side worked before my becm got wet, but the passenger's definitely did. Neither of them work now, although the lights come on on the switches. This is where it gets odd: When I switch on the LH seat heater, a relay inside the becm starts working very much like an indicator relay, although a little faster. If I now push "down" for one of the immobile windows, the relay stops clicking for as long as I hold the button!! Thus I believe the two problems are linked somehow.

4. Rear window demister:
Stopped working, although switch lights up.

OK, to the questions:
- Are any of the above functions associated with the big white multipin connector behind the RH front kick panel? Mine was green with corrosion and, even though I tried to clean it as best I could, I still suspect it.

- I have checked that I have power to all three main terminals on the becm. Could my problems still be related to the under-bonnet fuse box?

- Would it be possible to replace only the powerboard of the becm, thus negating the need for reprogramming?

- If the answer to the above question is yes, are the powerboards interchangeable between different issues of becm (i.e. could I use the powerboard from an AMR6531 with the logic board from an AMR5406)?

I hope someone can help.

Regards,
Henrik
 
Theoretically power boards should be interchangeable so long as both are from "H". Best bet is to PM Irishrover; if it's BECM, he's ur man!!
 
Sounds more like bad earths or contacts than a BECM problem to me. Worth checking the under bonnet fuse box. For the windows you really need a Faultmate to test what is and is not working. If the outstaion for the windows is shot that would cause the problem, the switch panel/outstation is a known problem.
 
Thanks guys,
So, are the rear windows run by the outstations in the front doors, or are there stations in the rear doors also?
I agree that bad earths could cause similar issues, but it's just too much of a coincidence to have this happen now, just after i bodged the becm, for it not to be related somehow. Both rear windows and rear screen demister were working fine before.

Henrik
 
Thanks guys,
So, are the rear windows run by the outstations in the front doors, or are there stations in the rear doors also?
I agree that bad earths could cause similar issues, but it's just too much of a coincidence to have this happen now, just after i bodged the becm, for it not to be related somehow. Both rear windows and rear screen demister were working fine before.

Henrik
I wouldn't like to list the number fo coincidental electronic failures that have happend in my work, usually caused by disturbing something not directly associated with the original problem:mad:
 
I wouldn't like to list the number fo coincidental electronic failures that have happend in my work, usually caused by disturbing something not directly associated with the original problem:mad:
I hear you.

So, are there outstations in the rear doors?


Cheers,
Henrik
 
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