LMC headlight harness quit working

Long time reader and follower, first time poster. I have not found any discussions about the issue that I am having, so I guess I have to ask the question.

I installed the LMC heavy duty headlight harness well over a year ago and it worked great. Before I installed the kit, my lights started to flicker one day. I didn't see any signs of melting at the pigtail or switch (and it looked like a previous owner had replaced it before), so I bought the kit instead. No problems at all until last week when it went out. High beams work, parking lights, dash lights, a LED rope light installed below the headlights and tied into the headlights all worked. I found it very odd that the rope lights worked but no headlights since they are tied into the headlight wiring and not the parking lights.

I hear a click in the relays like I should, and switched the relays to see if the low beam relay went bad, but still no change (high beams still worked, low didn't). I had some corrosion at the battery terminal where the harness tied in. Cleaned it, and part of the harness as well, still nothing. I removed the harness and went back to the original set up, and everything works again. I am leery of leaving it in its original set up since it had problems before, but cannot think of what could be wrong with the harness.

I think I have ruled out the relays, I don't see any breaks in the wiring, only place with any wear and tear is the wire going to the battery. Is there a fuse or something in the harness? Seems like there might be in the wire going to the battery. Any one else have any issues with the LMC harness? It was highly recommended on the forum when I originally bought it. Should I just replace the switch and use the original set up?

Any help is appreciated. BTW, I can usually problem solve most situations with my truck, but I am no mechanic or electrical expert at all.

Is it just the low beams that don't work then? To me it sounds like you either have a break in the wiring BETWEEN where the LED is spliced in and the connector or something is busted inside the connector.

An easy way to check and see if it's the first one is pull the bulb pot of the socket so you have better access and ruin then with the headlights on kind of wiggle and move that wire around just a little bit and see if there is any light. You should be able to get a little bit of contact from a broken wire and make it light as least slightly and temporarily. If not take a power probe light our multimeter and check for power in the socket. I'll find it real quick but I have a diagram that shows which is which

Edit: here we go, you'll have the 9004

And that's looking inside the connector that goes into the back of the housing, not the bass of the bulb

Thanks, that makes sense. Didn't even think about checking the LED wiring, but that very well could be it since it does not have soldered connections.

All other lights were working, just the low beams out, and since the LEDs were tied into the low wire and that plug was reused in the LMC harness, it makes sense that they are the only ones out.

What doesn't make sense is that it works again when not using the harness and the LEDs have not failed.

I'll have to check that out when I get some time in a few days.

iakshawks said:

Thanks, that makes sense. Didn't even think about checking the LED wiring, but that very well could be it since it does not have soldered connections.

All other lights were working, just the low beams out, and since the LEDs were tied into the low wire and that plug was reused in the LMC harness, it makes sense that they are the only ones out.

What doesn't make sense is that it works again when not using the harness and the LEDs have not failed.

I'll have to check that out when I get some time in a few days.

Click to expand...

Update?

I took a look at the wiring yesterday and unhooked the LEDs. When I did that the headlights still worked in the original stock setup, but still not with the harness. My wires were slightly different from the diagram in the fact that each of the three types were doubled so there were 6 total wires. I left the wires that had the LEDs connected to them loose (so I don't know if that is contributing to the problem). I plan on getting my voltmeter out later today or tomorrow to see where there is power. Obviously there is something since the headlights work in the original configuration. I'm thinking something went wrong with the harness.

Started to test from the battery to the bulb on the harness and I get power up to the relays, then nothing. The high beam has power after that when they are on, but not the low beams. Tried to switch the relays and same results. Makes me think there is a problem in the relay connector.

And my mistake on an earlier reply, the plug diagram above is the same, but still don't know if the cut extra wire makes a difference.