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Big Will

Odd electrical gremlin

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Hello all.

A few months ago I had a small hole welded approximately in the middle left side of the car roughly under rear seat's foot area. This was in preparation for a Dinitrol rust protection treatment (done by a reputable shop in Sweden as was the welding). I'm assuming the timing was coincidence but thought it's worth mentioning anyway. Shortly thereafter I began to occasionally get a warning that all of my rear lights were out (brake lights, tail lights, and license plate lights) although they all still worked. The problem began to happen more frequently recently.

Based on what I've read, it seemed like a problem with the CCM. I swapped it out for a used one of the same vintage but the problem re-occurred. This weekend I tried a third one that was working fine in the car it had been in but after a short drive, the same thing happened.

Any ideas or pointers?

 

  • All of the warning lights seem to go on at once or at least the tail lights and license plate lights and about 75% of the time also the brake light warning.
  • The lights all still function despite the warning.

 

Thanks for any ideas.

Edited by Big Will

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Was the welding work anywhere near a cable loom which could have been compromised?

 

In shipbuilding, we unplug digital systems in order to isolate them from induced voltages that may be generated as a consequence of welding.

 

We also restrict welding within a defined distance to digital systems in order to protect their electrical integrity.

 

Just a couple of left field ideas which could / may have had an impact.

 

On another track, the E28 check control system, when the rear light cluster lamp bases electrical connections oxidise and develop a high resistance can present as a warning light because of this high resistance, even though the lamps still function correctly.  Maybe consider some electrical contact cleaner for the rear end light circuits.  A leaking boot seal may well accelerate this process.  My assumption here is that the E34 is similar to the E28 just next generation.

 

Regards,

 

Mick

 

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Hi Mick. Thanks for the thoughtful reply.

With regard to the welding, that's interesting. I don't actually know if a wiring loom runs through/nearby under the carpet but I suppose there's a chance of that. I don't know what route the wire bundle takes from the CCM to the rear lights. Theoretically at least, this shouldn't have been a shade-tree welding job and at least the final product makes it hard to tell any work was done.

 

I'll check all of the bulb sockets this evening and see if hitting them with some contact cleaner makes for an easy fix.

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It may be worth seeing if unplugging the head lamp aim adjusters. I think the motors can fail and cause strange faults on the system. I remember this happening to mine and unplugging them did the trick. - easy to try at least

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As above. Try the adjusters. Just unplug them.

I also had an odd fault with cd changer being unplugged causing an issue but most likely adjusters.


Sent from my iPad using Tapatalk

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Thank you both for the suggestion. I will try unplugging the adjusters to see if that makes a difference.

 

Just a note - my headlight adjusters do currently work properly. My understanding was that if one or both weren't working and that caused the symptom of the warnings then it would indicate an issue with the LKM. Is that consistent with what you all have also experienced?

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Adjusters were my issue.

 

Have a look at CD changer too - i seem to recall either leaving it unplugged or it being plugged in cause me some odd symptoms though i'm hazy on that one, it was a long time ago!

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Thanks Duncan - always appreciate your ideas.

 

Just drove the iX from Berlin to the French Alps. Aside from the occasional phantom Check Control warnings the car drove nicely and averaged 10.1 L/100 with mostly Autobahn driving and some twisty mountain roads.

 

 

 

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