*DIY LKM Repair with pics

**zubbie** · 03-15-2008, 02:56 PM

I know there is a procedure on bmwe34.net... http://www.bmwe34.net/E34main/Mainte...trical/LKM.htm
but I thought I would add some pictures so that people can see exactly what fails and how easy it is to fix. As you know symtoms include low beams that turn off on their own and other sporadic behavior.

Once you have removed the LKM module from the car you have to extract the circuit board by carefully prying the edge of the case apart and sliding the connector / board assembly out.

Euro LKM

Prying the case apart

Board extracted

Other side, notice relays on both ends

Board out, relays down

Bad connections outlined in yellow

If you look closely at the above photo you will see that the relay solder connections have fractured and are not really soldered in any more. What you have to do is reheat them with a decent soldering iron and add a little more electronics grade silver solder. You need to add more solder as the flux in the new solder will help re-establish the connection so your LKM will work again. You can be anal and remove all the old solder and re-solder each connection but it's not really required. (I don't like solder suckers)

Look closely at the relays and be sure to touch up all the contacts (on both ends of the LKM)

If you haven't ever soldered before then Google it. Its not hard

http://www.aaroncake.net/electronics/solder.htm

Hope this helps some of you

**r1101r** · 03-15-2008, 03:01 PM

this should be added to the diy sticky.

**attack eagle** · 03-15-2008, 05:46 PM

ditto.

**zubbie** · 03-15-2008, 09:42 PM

request for add to DIY posted

**lilxedith** · 03-15-2008, 10:03 PM

where was this module pulled from?

**zubbie** · 03-15-2008, 10:35 PM

Originally Posted by lilxedith

where was this module pulled from?

On my 535 it's in the fuse box located on the drivers side firewall in the engine compartment

**bmwpower** · 03-16-2008, 01:18 AM

Thank you!!

bmwe34.net is great, but a lot of the time the pictures just suck. Yours are great.

(1) Can you remove the LMK with the car off or do you have to undo the battery? Stupid question, but it is a module after all.

(2) The 4 relays...what are they responsible for? Which ones are responsible for which lights?

**attack eagle** · 03-16-2008, 01:44 AM

If I am not mistaken, one is headlights high, one low, and one for front fogs.
euro spec cars would have had an additional relay for rear fogs.

**bmwpower** · 03-16-2008, 01:47 AM

Originally Posted by attack eagle

If I am not mistaken, one is headlights high, one low, and one for front fogs.
euro spec cars would have had an additional relay for rear fogs.

So what about the 4th? Or do all LKM's have 4 relays no matter if they use the 4th or not?

**attack eagle** · 03-16-2008, 01:57 AM

he's in C, eh. N, eh. D, eh.

They may have all LKMs that are Euro spec.

that one says LKM-B (basic) and ECE (=euro if my brain is working tonight?)
most of the ones I see for sale in the US say LKM-L (luxury) US.

**zubbie** · 03-16-2008, 07:25 AM

Originally Posted by attack eagle

he's in C, eh. N, eh. D, eh.

They may have all LKMs that are Euro spec.

that one says LKM-B (basic) and ECE (=euro if my brain is working tonight?)
most of the ones I see for sale in the US say LKM-L (luxury) US.

Partly. My car is a Japan import, thus the LKM-B ECE (euro). Normally it would be the same as all the other US vehicles.

And yes I have rear fogs..and high beam / front fogs can be on simultaneously

**ThreeM30s** · 03-16-2008, 08:20 AM

Ahh yes, the old worn out LKM problem...

Nice pics, but does this repair also solve the mysterious non-fading interior lamp (10-15s after door close) problem?

**zubbie** · 03-16-2008, 08:49 AM

Originally Posted by ThreeM30s

Ahh yes, the old worn out LKM problem...

Nice pics, but does this repair also solve the mysterious non-fading interior lamp (10-15s after door close) problem?

I wasn't aware of this problem. IF it is the LKM that controls this function, then my knowledge of electronics would say that it would not solve it. The relays are only for exterior lights. I would suspect another component is the culprit. Without the schematics of the control circuitry it would be hard to guess. A simple dimmer circuit looks like this. I note one capacitor here which are normally the culprits (leak out) . I also noticed only one cap on the LKM...interesting

You could always replace the cap in the LKM and see...

Dome light automatic dimmer circuit

**bmwpower** · 03-16-2008, 09:08 AM

Mine doesn't fade, but it does go out after a little while. Is that the problem?

**robmpulse** · 03-16-2008, 10:50 AM

Originally Posted by bmwpower

Mine doesn't fade, but it does go out after a little while. Is that the problem?

No, I think only later models faded out, and the earlier ones just shut off.....

**slocar** · 03-16-2008, 03:24 PM

Originally Posted by robmpulse

No, I think only later models faded out, and the earlier ones just shut off.....

I was under the impression that all LKM-Ls faded, LKM-Bs just shut off. I could be wrong though.

**zener** · 03-16-2008, 03:51 PM

LKM doesn't control interior lights. General Module and Relay Module together under rear seat does.

**Binjammin** · 03-16-2008, 03:51 PM

Originally Posted by attack eagle

he's in C, eh. N, eh. D, eh.

They may have all LKMs that are Euro spec.

that one says LKM-B (basic) and ECE (=euro if my brain is working tonight?)
most of the ones I see for sale in the US say LKM-L (luxury) US.

I was reading eh as the letter H. Man, I was so confused, I wanted to hurt you as much as my brain hurt. I have teh dumb today.

**bmwpower** · 03-16-2008, 07:53 PM

G*ddamnit...how do you pull this thing out? I'm sitting here trying to do it now and it doesn't want to budge.

Help?!?

**slocar** · 03-16-2008, 08:08 PM

Originally Posted by bmwpower

G*ddamnit...how do you pull this thing out? I'm sitting here trying to do it now and it doesn't want to budge.

Help?!?

Pull harder of course ... that's the answer to removal of 99 percent of parts on our cars.

**bmwpower** · 03-16-2008, 08:16 PM

Originally Posted by slocar

Pull harder of course ... that's the answer to removal of 99 percent of parts on our cars.

Got it! I had to rock it back and forth a little. Looks like mine is a rebuilt unit.

**slocar** · 03-16-2008, 10:44 PM

I have a unit that was rebuilt by Programa in 2004 or something like that. Needless to say, I'm not expecting it to fail as long as I have the car.

**E34Mekanik** · 03-17-2008, 02:35 AM

Why does everyone have 4 relays and I only have 3!!! Got carried away and resoldered the entire thing. It was fun. My facelifted LKM seems to like new HIDs, hopefully they will be friends forever. I still get the low beam ding, why?

**bmwpower** · 03-17-2008, 02:40 AM

Mine has 3. Mine is a rebuilt unit. One of the relays is black (new style?). I resoldered mine tonight, too.

**zubbie** · 03-17-2008, 07:28 AM

The standard 3 relays are (as stated above) Low beam, High Beam and Fogs. The 4th relay is for the rear fogs on Euro cars

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