Headlight failure, LKM repair

[Crewblunts]

I was looking on bmwe34.net and reading the instructions on fixing the LKM. However when I opened the module there were only three relays. It is a 1990 535i. should I just go ahead and try to resolder the three relays that are there? It does not look like any fell or were knocked off. The are no pins in the solder underneath where the 4th relay should be and there are no pieces anywhere to be found. It is one of the inside relays if it makes a difference. Thanks in advance for the help all.

-Phil V In CT

[Tiger]

Low Beam, High Beam and Foglight = three relays... with the cover off and plugged in, activate the one of the relays that are together next to each other... just resolder the one that activates your low beam. What happens is over time the solder cracks and sometime doesn't turn on one or the other headlight.

[Crewblunts]

Thanks a million Tiger I will do that. I was rather confused and really appreciate the help.

-Phil V

[InfernoM3]

Thanks a million Tiger I will do that. I was rather confused and really appreciate the help.

-Phil V
I tried this the DIY on Brunos site and I still didn't work. My passenger low beam has been out for a month on my 90 525i. ANyone have some advice. the low beam is the furthest relay on corner right? I really don't want to forkout 100-300 for a new lkm.

[Phil Sanderson]

Check your headlight fuse or fuses in the fusebox. Inside the fusebox lid will tell you which ones to look at. Replace the fuse with a different one to make sure. Hope this helps

[Unregistered]

Just tonight I pulled my LKM and I too found only 3 relays. Since I did not have any low beams, I figured nothing to lose so I resoldered (actually reflowed) all the relays and the solders around them. I used a needle point iron and when I reflowed the joints, I just touched the point to the joint and as soon as it "rippled" I got off it. I did not have to add any solder to any joints.


Put it back together and plugged it in and now have headlights. (Low beams were out actually, all the rest worked).

Mike Holbrook
Spring Valley, CA

[Warren N.CA]

I was looking on bmwe34.net and reading the instructions on fixing the LKM. However when I opened the module there were only three relays. It is a 1990 535i. should I just go ahead and try to resolder the three relays that are there? It does not look like any fell or were knocked off. The are no pins in the solder underneath where the 4th relay should be and there are no pieces anywhere to be found. It is one of the inside relays if it makes a difference. Thanks in advance for the help all.

-Phil V In CT

[Warren N.CA]

The problem is "cold solder joint" syndrome. It means that the large terminal was not heated enough during the solder process for a proper molecular bond to be formed. But it was touching the terminal, so it worked for a while. Then, over time, with temperature changes, the solder stopped contacting the relay terminal, tearing down the elecrical connection.

This is a common problem with circuit boards that have been soldered by an automated "solder bath" process. The heat was simply inadequate to heat through the LARGE terminals, but the small ones are OK.



Low Beam, High Beam and Foglight = three relays... with the cover off and plugged in, activate the one of the relays that are together next to each other... just resolder the one that activates your low beam. What happens is over time the solder cracks and sometime doesn't turn on one or the other headlight.

[Bill R.]

some have 3, but if you notice on the schematic for the 3 relay lkms, that the headlight relay is a double pole double throw instead of a single like the 4 relay boards, so you still have a set of contacts for each low beam and a terminal soldered on the board for each one too...so in effect they combined 2 relays into one on the 3 relay board.










I was looking on bmwe34.net and reading the instructions on fixing the LKM. However when I opened the module there were only three relays. It is a 1990 535i. should I just go ahead and try to resolder the three relays that are there? It does not look like any fell or were knocked off. The are no pins in the solder underneath where the 4th relay should be and there are no pieces anywhere to be found. It is one of the inside relays if it makes a difference. Thanks in advance for the help all.

-Phil V In CT

[Unregistered]

Low Beam, High Beam and Foglight = three relays... with the cover off and plugged in, activate the one of the relays that are together next to each other... just resolder the one that activates your low beam. What happens is over time the solder cracks and sometime doesn't turn on one or the other headlight.


I was playing around with the klm and messed it up! Where can I get a cheap one?

Thanks!