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Discussion Starter #1 (Edited)
Went to start the car again saturday night after a short drive to a friends, when suddenly Dip Beam appears on the dash and the low beams are dead.

All other lights were fine.

Suspected the LKM (light control module) as these develop a common fault; dry joints appear on the relays for the low beam and need resoldering.

To the astonishment of my passenger I pulled out another two LKMs from the glovebox, (he said I need to get out more!), and plugged on in. No joy, so plugged old LKM back in.

Abandoned car and went out on the town via taxi.


Next day took car home and changed a front bulb to test. Didn't look blown and didn't light up. Noticed one 7.5amp fuse for low beam was blown, so replaced. Lights came on for about half a second, then noticed both 7.5a fuses had blown again.

Replaced both fuses and put the newer LKM in. Works a treat. Looks like the original unit has developed a serious fault. Won't use that again.





There are two distinct versions of the LKM, one is a single board unit and was generally used since 1992. Oddly my 1991 built car had one of these when I got it.

I picked up a spare single, and also a dual board (1988-1992) version from an earlier E34 non-M5, and resoldered it, but had not tested it. I bunged that in and it appears to work, all the lights bar the problemmatic low beams functioned. I reverted to the single board one I have anyway.




These boards are fairly freely available from most scrapyards, I generally pay £5, 10 or £15 depending where I go. Resoldering them is a much more cost effective solution than a brand new one from BMW as they are quite expensive. Resoldered units tend to last about a year to eighteen months in daily use before requiring repair again.



Resoldering is quite easy, just open the case, multiple levers or small flatblade screwdrivers required to lift all the catches off, then slide it out.

You will likely see solder joint cracks or dry joints on the underside of the board directly below the low beam relays which are mounted on the top edges of the board, easy to locate as big compared to other components.

The procedure is covered here on the BMWE34.net website


Ivan.
 

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Ah the good old days of E34 ownership...................

If only life was that simple now................

ouich
hiha:7:
 
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