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SavageXii

E34 540I Strange Dimmer/Interior background lighting problem

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Hi all,

Bought a new car, next day driving out the driveway, noticed my driver side headlight was out but park lights were still on, thought it was just a bulb, however the background lighting to the dash/cluster and radio/obc/ac controls started to flicker, leaving the cabin pitch black. after flickering back on, my headlight came back as normal. Now I notice when Indicate or brake or reverse I can make the flickering happen on purpose.

Does anyone have idea's on what to check or have stumbled across this problem before? My guess is a loose wire in the light switch or a bad ground or a bad fuse/relay?

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Does it change at all with revs or when driving, what it does do with just park lights on? Battery good and cable grounds clean and tight? LKM under the hood and dimmer switch on the dash can play up causing weird light behavior

Quick check of the wiring under the steering wheel, seat and boot\bootlid and reseatiing plugs and modules doesn't hurt

 

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LKM is definitely a possibility with this weird behavior.

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lkm is a known problem on e34s may need to reflow the solder

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13 hours ago, Eagle said:

Does it change at all with revs or when driving, what it does do with just park lights on? Battery good and cable grounds clean and tight? LKM under the hood and dimmer switch on the dash can play up causing weird light behavior

Quick check of the wiring under the steering wheel, seat and boot\bootlid and reseatiing plugs and modules doesn't hurt

 

Don't believe its rev or driving related just when other lights eg brake and indicator come on, new battery, will check battery ground and boot ground and try to find headlight ground, not sure where the others ground.

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13 hours ago, turbolizard said:

LKM is definitely a possibility with this weird behavior.

Had all the Check control errors for all the lights, put in a used lkm and those went away, but had the same issue with the old lkm, and still present with the seemingly good lkm

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interior dash lights can be a bad dimmer control dial unit , 

head lights , i would be looking at all the ground conections in the engine bay , 

positive conections at the battery and engine bay etc 

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i cant recall the symptoms but one of the above posts also reminded me that where the wiring goes from the car body into the boot lid(it is strapped to one of the hinges) can cause short circuits there.You mentioned some problems with brake or reverse lights which are on the boot lid?

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It all seems to be related, as after flickering the headlight came back on, and happens on command by putting in reverse with brakes held on or indicating while driving.
Is there a common ground or shared circuit for headlights/indicators/brakes/reverse/dimmer?

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i cant say sorry.Google some of your symptoms there are still some very good e34 resources and dedicated forums.

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11 hours ago, kiwi535 said:

i cant say sorry.Google some of your symptoms there are still some very good e34 resources and dedicated forums.

I've had quite a extensive look online, turns out I think it was a problem with the LKM, the new one I thought was good turned out to be better (no check control spasms) but retained the headlight and dimmer problem so I thought I had eliminated the lkm issues but sadly not!

Would be good to see a perfectly soldered LKM, as some of the pins are bridged I dont know if that is normal or if they got hot enough to reflow and bridge

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