lmc HD headlight harness gmc/4 lights

[nrb's70gmc]

Here is how the lmc harness looks (becouse of the yellow cover) there are 2 black wires that i cant tell ware they go. this is as to the best of my knowlage lol with the yellow cover still on the harness (the original harness plug has brown/white & green/white striped wires.

[DaBigKahuna]

ok... the relays should be the same. Un plug the high beam relay and test the low beam relay.

I would check for power on the low beam side of all for plugs and also check to make sure that you don't have power on the high beam side.

[nrb's70gmc]

Originally Posted by DaBigKahuna

ok... the relays should be the same. Un plug the high beam relay and test the low beam relay.

I would check for power on the low beam side of all for plugs and also check to make sure that you don't have power on the high beam side.

well i did the opposite i think, i tested the 2 outside 3 prong low/high lights
i plugged the the low beam relay. and test lighted and this is what happens


1, low beam power to outside lights green wire (center post) but also power to the 2 prong high only plug.

there is 2 green wires off the back of the 3 prong plug( both are connected to the center low beam post), (one goes to the low beam) and the other jumps over to the high beam post on the 2 prong (high only) plug. the 2 prong plug only has a black ground and the green low beam wire that jumps from the 3 prong plug.

the high beam (tested) is the tan wire on the 3 prong plug

2, while the low beam relay is plugged in and all 4 lights, the lights on low the inner (2 prong) plugs look to be on full power low--while the outer lights are also on very dim. while on low only the 2 outer lights are supposed to be on.

[nrb's70gmc]

Just to make sure this is not wrong, (as directions say) i plugged the the hd harness into the factory harness plug nearest the battery (passenger side) is that whare it should be?

or should it be plugged in to the driver side?
as you can see in the drawing the hd plug harness wires dont even match the factory, the green and tan wires are reversed.

[jtj143]

I bought the same harness from LMC and I am getting the same results as you. All four lights are on, although two of them extremely dim.

I called LMC to verify that the harness is correct, I thought maybe I had gotten a Chevy 2-light harness by mistake. I also inquired as to why the hardware listed in the instructions doesn't match the hardware included on the harness. The LMC rep. checked some sort of archive and said that the single three prong connector is correct and that if I want to return the harness, it may not be altered.

Hope a solution presents itself, I am looking forward to vivid night driving!

[nrb's70gmc]

Originally Posted by jtj143

I bought the same harness from LMC and I am getting the same results as you. All four lights are on, although two of them extremely dim.

I called LMC to verify that the harness is correct, I thought maybe I had gotten a Chevy 2-light harness by mistake. I also inquired as to why the hardware listed in the instructions doesn't match the hardware included on the harness. The LMC rep. checked some sort of archive and said that the single three prong connector is correct and that if I want to return the harness, it may not be altered.

Hope a solution presents itself, I am looking forward to vivid night driving!

Now i dont feel so stupid -how hard is it to plug in a plug in play harness-- please keep in touch with what you find out--there is somthing bonkers in that harness if lmc says its the right one.

[DaBigKahuna]

Ok ... I've looked at that wiring diagram that you posted and it just looks wrong.

Let me rephrase that.. it looks like it's consistant with the results you are getting and not with the results you want.

Why would you run the same power to the low beam on the outsides and to the high beams on the insides. It should wire just like the pic you posted of the original wiring.

The relays are nothing magical. Instead of the light switch energizing the light themselves, it energizes the relays which in turn energize the lights.

[nrb's70gmc]

Originally Posted by DaBigKahuna

Ok ... I've looked at that wiring diagram that you posted and it just looks wrong.

Let me rephrase that.. it looks like it's consistant with the results you are getting and not with the results you want.

Why would you run the same power to the low beam on the outsides and to the high beams on the insides. It should wire just like the pic you posted of the original wiring.

The relays are nothing magical. Instead of the light switch energizing the light themselves, it energizes the relays which in turn energize the lights.

hay man thats how the lmc hd harness is wired believe me it does not make sence to me either, im going to address that issue first.

i figured there would be a wire jumped from the 3 prong high beam(outer) to the 2 prong high beam (inner).

however, do they sell those light plug terminals at napa? i figured i would pick some up.

[nrb's70gmc]

im going to move the jumper wire from the 3 prong low that goes to the 2 prong high
i think the jumper wire is supposed to be connected to both high beam teminals (at least that makes sense.)

[nrb's70gmc]

well i broke one of the terminals trying to get it out of the plastic light plug, so everythings on hold untill i get to the parts store.

[nrb's70gmc]

by the way does anyone know a part# for those 90 degree female terminals that go in the headlight plugs?

[DaBigKahuna]

Originally Posted by nrb's70gmc

im going to move the jumper wire from the 3 prong low that goes to the 2 prong high
i think the jumper wire is supposed to be connected to both high beam teminals (at least that makes sense.)

Sounds reasonable to me!

Normally the spade connectors in the plugs would have a tab bent out to lock them into place. if you want to move them, you may need to push that tab in so you can slide the connector out the back.

Also Make sure that the grounds are in the right location on the plugs.

[jtj143]

Ok, I got it!
Disregard the wire labels and the instructions that came with the upgrade kit. The green wire on the high bulb (inside two terminal) should be paired with the BROWN wire on the low bulb (outside three terminal). I've done this and bench tested it - it works great! I'll get it all more permanently wired and the bulbs fastened in tomorrow.

Hope this helps nrb!!

It's a pretty simple fix. But to pay $30 + shipping for a kit, then have to modify it just to make it operate as advertised - not pleased with LMC.

[DaBigKahuna]

Originally Posted by jtj143

It's a pretty simple fix. But to pay $30 + shipping for a kit, then have to modify it just to make it operate as advertised - not pleased with LMC.

Agreed!

[nrb's70gmc]

Originally Posted by DaBigKahuna

Sounds reasonable to me!

Normally the spade connectors in the plugs would have a tab bent out to lock them into place. if you want to move them, you may need to push that tab in so you can slide the connector out the back.

Also Make sure that the grounds are in the right location on the plugs.

well like i said- i broke the first terminal trying to get it out--so no matter what i need another one and my local auto shops dont carry the 90 degree spade terminal. Ya even though lmc does not make this harness there going to be the ones blamed for it.

[nrb's70gmc]

Originally Posted by jtj143

Ok, I got it!
Disregard the wire labels and the instructions that came with the upgrade kit. The green wire on the high bulb (inside two terminal) should be paired with the BROWN wire on the low bulb (outside three terminal). I've done this and bench tested it - it works great! I'll get it all more permanently wired and the bulbs fastened in tomorrow.

Hope this helps nrb!!

It's a pretty simple fix. But to pay $30 + shipping for a kit, then have to modify it just to make it operate as advertised - not pleased with LMC.

thanks for the tip- (you got to it before i did lol) as soon as i get another 90 degree spade terminal i will do the same

[nrb's70gmc]

Originally Posted by jtj143

Ok, I got it!
Disregard the wire labels and the instructions that came with the upgrade kit. The green wire on the high bulb (inside two terminal) should be paired with the BROWN wire on the low bulb (outside three terminal). I've done this and bench tested it - it works great! I'll get it all more permanently wired and the bulbs fastened in tomorrow.

Hope this helps nrb!!

It's a pretty simple fix. But to pay $30 + shipping for a kit, then have to modify it just to make it operate as advertised - not pleased with LMC.

ok ilgot it to, worked on it today and i see the light (test light) i bought 4 new h4 pigtails and wired them in the (right way)

2 lows come on then all 4 highs come on

its 33 degrees out side and dark so im going to wait till the morning to put the lights in.

[jtj143]

I am extremely pleased with the performance of this headlight upgrade! The bright lights are super bright!

I contacted LMC by mail - you know, an old fashioned letter. In an envelope. With a postage stamp.

A representative from LMC left a telephone message yesterday morning and we played phone tag all day after that. Finally this morning I spoke with Raina. She was very nice and very understanding. Raina said that she will have the product development team take a look at their heavy duty harness upgrade to see if perhaps they received a bad batch, or if there is some other broad problem with the manufacturing of these. She also said that LMC will refund me the purchase price. This is acceptable to me, hopefully the next customer will not have to deal with the frustrations that NRB and I had to deal with.

[bbadfred]

Have same problem gonna try the green brown wire thing. If that does not work, Then we are planning on butchering the LMC harness using wiring diagrams posted by others about this same problem on the forum
I have talked to LMC numerous times and they know less about the harness than I do! the step3 and step5 alternate instructions keep telling me to hook up stock wiring to plugs that are not on the harness!!! Ours did work cept it back feeds to the high beam indicator on the dash.

[parrotheadmatt87]

So I'm confused on what to bypass? Or switch? Maybe if you drew another sketch showing what to change that would help I don't want to screw my harness up. Thanks

[parrotheadmatt87]

So is this how its done?

http://www.flickr.com/photos/29856692@N02/6873584704/

[davepl]

I got the same harness from the same vendor, same problem. They're all wired wrong. If you search through my posts I detailed it a while back.

Long story short you can pop the connectors out of the harnesses at the headlights and re-insert them in the correct positions. They use green and brown wires, the same colors as the factory wires, so I just made it all match up to the factory connectors.

From there I wired the brown "trigger" into the brown of the factory harness and the green "trigger' into the green of the factory harness. After that it all worked fine.

I wasted a good hour on this thinking I must be doing something wrong. Not that I'm glad you had the same problem, but I'm glad to find out I wasn't nuts!

[parrotheadmatt87]

I searched through your post and I couldn't find what thread you were speaking of. I popped out the wires on the connector that plugs into the existing harness and matched brown to brown black to black and green to green. I was able to get all the high beams to work and the lows worked but the middle lights would come on during low beam operation but just barely. Then I ran the high beams for a few seconds and switched it back and the low beams stopped working. I looked at the relays I fried one of them. I assume its the one that works for low beams since they're inop. Could you explain in detail which wires you switched and where? I just want my truck lights to be operational I just got it and I cant drive it sadly. Thanks for all the help.

[bbadfred]

Originally Posted by davepl

I got the same harness from the same vendor, same problem. They're all wired wrong. If you search through my posts I detailed it a while back.

Long story short you can pop the connectors out of the harnesses at the headlights and re-insert them in the correct positions. They use green and brown wires, the same colors as the factory wires, so I just made it all match up to the factory connectors.

From there I wired the brown "trigger" into the brown of the factory harness and the green "trigger' into the green of the factory harness. After that it all worked fine.

I wasted a good hour on this thinking I must be doing something wrong. Not that I'm glad you had the same problem, but I'm glad to find out I wasn't nuts!

Yes after I last posted we were looking at the harness and noticed that same thing that the colors were switched, as soon as we matched harness colors switching the factory plug to the lmc harness they work super!!!

[C5Phil]

OK... I have the same lmc harness with the same issue (dim lit blubs on sometimes) on my GMC... I tried to follow this thread but got confused real quick-- the way I read through it there seems to be posted multiple solutions...Am I wrong? in any case I can't follow any of them (yes I'm electrically illiterate) could someone give me simple step by step instructions on how to install the screwed up LMC harness in to my 70 GMC? i'd be forever grateful.....
And I bet this would make a great sticky in the FAQ section--