lmc HD headlight harness gmc/4 lights

[bbadfred]

Originally Posted by nrb's70gmc

i went and checked the wires on the lmc harness and somthings messed up arrording to the pic above.

looking at lmc harness the 3 prong plugs head on from front there are 2 GRRENwires coming out the center post one BLACK from the left and a BROWN wire coming out the right

on the 2 prong plugs from front 1GREENwire left and 1 BLACK wire from right.

i dont know why this lmc harness is wired like that (if wrong)

I matched the colors on the harness to the driver side truck plugin and they all work fine! green to green brown to brown and black to black

[C5Phil]

Originally Posted by bbadfred

I matched the colors on the harness to the driver side truck plugin and they all work fine! green to green brown to brown and black to black

Please don't get frustrated with me... but doesn't the LMC harness plug into the PASSENGER side OEM harness? So should I match up the OEM (female) wires with the (male) LMC harness? If so, This means I will need to purchase a male harness end since the LMC harness is molded firmly around their wires.... correct? If not correct or if the results are the same, I can remove the female OEM wires and move them to correspond with the LMC connector....??? Am I even close to being correct??

I really, really, really appreciate ANY help I get with this-I've beden stymied with this issue for about a month.....

[parrotheadmatt87]

The wires on the LMC harness do plug in to the last harness closest to the battery or passenger side. Now if you look at the original harness that plugged into the back of your headlight you will see a 3 prong connector one wire will be brown one will be black and the other will be green. Off the top of my head I cannot remember the wire layout but do what the others have said. You can remove the wires from the LMC harness. What you have to do is using a small flat head screw driver you run the tip of it next to where the wire goes (dont worry you wont break the terminal so shove it in pretty deep then remove the screwdriver), and with the other hand tug on the wire till it pops out. I know one of the wires I had to swap was difficult to remove I had to take a bigger flat head and turn it slightly and put pressure on the terminal to pop the wire out. Once you get those wires out look at the metal male terminals. If you look closely you will see a small slit push that slit out so its raised (thats what holds the terminal inside the connector), and push it into the correct location it should click into place. Once you push the wire in tug a little on it to make sure it clicked back into place. Once you get that correct it should work without any issues. If I get a chance tomorrow I'll post pictures on how I have mine so that way people will see how the wires are supposed to go. Oh btw make sure that when you are matching up the wires you remember that since the harnesses clip into each other they will be mirroring each other so i.e. if the right wire on the truck harness is green you would put the green wire on the lmc harness on the left so when you connect it the wires will be color matched face to face. If that makes sense. Hope this helps I should have posted and update.

[C5Phil]

Originally Posted by parrotheadmatt87

The wires on the LMC harness do plug in to the last harness closest to the battery or passenger side. Now if you look at the original harness that plugged into the back of your headlight you will see a 3 prong connector one wire will be brown one will be black and the other will be green. Off the top of my head I cannot remember the wire layout but do what the others have said. You can remove the wires from the LMC harness. What you have to do is using a small flat head screw driver you run the tip of it next to where the wire goes (dont worry you wont break the terminal so shove it in pretty deep then remove the screwdriver), and with the other hand tug on the wire till it pops out. I know one of the wires I had to swap was difficult to remove I had to take a bigger flat head and turn it slightly and put pressure on the terminal to pop the wire out. Once you get those wires out look at the metal male terminals. If you look closely you will see a small slit push that slit out so its raised (thats what holds the terminal inside the connector), and push it into the correct location it should click into place. Once you push the wire in tug a little on it to make sure it clicked back into place. Once you get that correct it should work without any issues. If I get a chance tomorrow I'll post pictures on how I have mine so that way people will see how the wires are supposed to go. Oh btw make sure that when you are matching up the wires you remember that since the harnesses clip into each other they will be mirroring each other so i.e. if the right wire on the truck harness is green you would put the green wire on the lmc harness on the left so when you connect it the wires will be color matched face to face. If that makes sense. Hope this helps I should have posted and update.

it makes sense-but only one issue- I just tried it- I moved the lmc wires from their original positions to match with OEM pass. side three prong headlight harness connector - result was as follows:

When dash indicator on low beam- two outside headlight blubs on normal- two inside blubs on dimmer,
When dash indicator on high (red light on)- two inside blubs on normal- two outside blubs on dimmer.

Aren't they all supposed to be on in high beam mode and only the low beams on in low beam mode?

Seems that I'm missing a step... does one wire need to be spliced into another (a previous post mentioned that as part of a fix)-????

Again I have basic wiring knowledge and so far what I've done isn't rocket science but I must be missing something...

Thanks in advance-- Phil

[bbadfred]

Originally Posted by bbadfred

I matched the colors on the harness to the driver side truck plugin and they all work fine! green to green brown to brown and black to black

My battery is mounted on the drivers side (so that I would have room for the aftermarket 4" intake tubing and air filter on the right). So I used the Drivers side 3 prong plug (all other stock headlight wires are removed). the black wire is grounded on the radiator support and the LMC harness 3 prong male plugin wires were matched to the truck plug. I have two outer bulbs on low beam and all four on high beam. the rest of the LMC harness is installed normally thru the relays and plugged into the provided headlights and plugins. when it was wrong it worked but the high beam indicator light on the dashboard was bright on lowbeams and barely glowed on hi beam. As soon as we matched the wire colors everyting worked fine including hibeam indicator on the dash.

[C5Phil]

The Drivers side connectoryou used is the one for the three prong headlight bulb, correct? I did the same - just used the Pass. side one- all others are unused-- Mine still has the "dim" bulb issue....

[bbadfred]

Originally Posted by C5Phil

The Drivers side connectoryou used is the one for the three prong headlight bulb, correct? I did the same - just used the Pass. side one- all others are unused-- Mine still has the "dim" bulb issue....

yes,I just can't think of anything else I did different? I have after market gauges and a homemade dash wiring harness with led bulbs for turn and hibeam indicator but i used the factory wires for the power to the dash lights.?

[bbadfred]

Originally Posted by bbadfred

yes,I just can't think of anything else I did different? I have after market gauges and a homemade dash wiring harness with led bulbs for turn and hibeam indicator but i used the factory wires for the power to the dash lights.?

One thing I never had was dim lights they just did not work correctly.

[C5Phil]

Well from what I can figure I have the same issue as nrb's70GMC --

so .......

As I understand it all I need to do is move the green wire on the two prong bulb that connects the high beam and low beam blubs from the green terminal on the three prong bulb to the brown terminal on the three prong bulb-- I need to do this for each side (Pass. and Driver side bulbs).

I PM'd nrb's70 GMC and if he confirms I'll rip into that POS LMC harness-
BTW I called LMC- their advice-- check the grounds and power supply....when I asked to speak with the tech adviser who sent that piece of advice they told me the tech dept. only communicated with the Customer Service Rep's-- never the customers... go figure.....

[C5Phil]

Originally Posted by C5Phil

Well from what I can figure I have the same issue as nrb's70GMC --

so .......

As I understand it all I need to do is move the green wire on the two prong bulb that connects the high beam and low beam blubs from the green terminal on the three prong bulb to the brown terminal on the three prong bulb-- I need to do this for each side (Pass. and Driver side bulbs).

I PM'd nrb's70 GMC and if he confirms I'll rip into that POS LMC harness-
BTW I called LMC- their advice-- check the grounds and power supply....when I asked to speak with the tech adviser who sent that piece of advice they told me the tech dept. only communicated with the Customer Service Rep's-- never the customers... go figure.....

Just got a call from LMC- they are sending me another harness-- I'll let all know if it is "different" from my current one--- if not it's the "green wire"mod for me.....stay tuned

[parrotheadmatt87]

Make sure all the other wires are matched up color to color on the rest of the terminals I cant remember if I changed the others or if it was just that one on the end. I know at one point I had the low beam terminals upside down so I flipped the terminal upside down and had no issue but I did that before I turned it on.

[bgwss]

Originally Posted by C5Phil

Just got a call from LMC- they are sending me another harness-- I'll let all know if it is "different" from my current one--- if not it's the "green wire"mod for me.....stay tuned

Inquiring minds want to know.

[C5Phil]

I posted earlier that Customer Service at LMC was going to send me another HD harness- Well, it showed up today and unfortunately it is wired exactly like the first one-- I think they thought if they threw another harness at me I'd quit complaining-- well they got it half right-- I'll quit contacting them but I'll still complain to anyone willing to listen.... going to try the green wire move next---

[C5Phil]

Did the green to brown wire move-- now no headlights at all....

[C5Phil]

Originally Posted by C5Phil

Did the green to brown wire move-- now no headlights at all....

Found a loose ground-- headlights working but still have din inside bulbs when high beam indicator on.. all four light bright when low beams on... something is backwards-- homing in on issue- stay tuned--

[chalet2506]

Dredging this one up. Didn't realize this harness was such a pita when I ordered it, but figure I might as well make it work.

1st thing. Its been about a year and a half since I drove the truck and I don't remember how the oe headlights work. Inside and outside bulds lit up on bright, and outside only on dim?

C5phil did you figure it out? I have the same problem. I went with custom dashes and don't have a high beam indicator hooked up yet. Matched the wire color positions on the plug from the oe harness to the LMC Harness. But 1st switch position I had everything lit up. 2nd switch position I got bright outside(3 prong bulb) and very dim inside lights.

So driver side I moved the green / brown wires on the the 3 prong bulb on driver side to match the color position on the original plug. Now on that side I have everything lit up in 1st position still, but dim and very dim on 2nd switch position.

Truck is a 72 GMC Jimmy

[davepl]

In my case I just popped ALL the connections out of the headlight style connectors on the harness and redid them by following the factory color scheme. The harness has green and brown wires, as does the factory harness.

Basically one of your factory harness green wires winds up triggering a relay that powers all the green wires, which in turn connect to the headlights where the original green wires did. Same deal for the brown. I followed that basic rule and it all worked first time when I reconnected everything.

[chalet2506]

Thanks. I'll give that a try.

[C5Phil]

Originally Posted by chalet2506

Dredging this one up. Didn't realize this harness was such a pita when I ordered it, but figure I might as well make it work.

1st thing. Its been about a year and a half since I drove the truck and I don't remember how the oe headlights work. Inside and outside bulds lit up on bright, and outside only on dim?

C5phil did you figure it out? I have the same problem. I went with custom dashes and don't have a high beam indicator hooked up yet. Matched the wire color positions on the plug from the oe harness to the LMC Harness. But 1st switch position I had everything lit up. 2nd switch position I got bright outside(3 prong bulb) and very dim inside lights.

So driver side I moved the green / brown wires on the the 3 prong bulb on driver side to match the color position on the original plug. Now on that side I have everything lit up in 1st position still, but dim and very dim on 2nd switch position.

Truck is a 72 GMC Jimmy

i hate to be a downer-- but I tried and tried to fix my LMC harness never could getit correct-- I have limited electrical knowledge- so I ended up going with a harness from these guys--

http://67-72chevytrucks.com/vboard/s...d.php?t=535233


never been happier- works like a charm and was a perfect plug and play- LMC just kept giving me the run around- even sent me another harness- it functioned the same as the old one- like crap!!! Hope you get your lights sorted out -- Good Luck

[C5Phil]

PS. as referenced in my previous post-- Anyone want to buy a brand new in the original packing LMC heavy duty headlight harness for a GMC? LOL

[GMCJOE]

Originally Posted by C5Phil

PS. as referenced in my previous post-- Anyone want to buy a brand new in the original packing LMC heavy duty headlight harness for a GMC? LOL

I pay the shipping if you want you just want to give it away...

[chalet2506]

Originally Posted by davepl

In my case I just popped ALL the connections out of the headlight style connectors on the harness and redid them by following the factory color scheme. The harness has green and brown wires, as does the factory harness.

Basically one of your factory harness green wires winds up triggering a relay that powers all the green wires, which in turn connect to the headlights where the original green wires did. Same deal for the brown. I followed that basic rule and it all worked first time when I reconnected everything.

That did it. Just make sure get the ground on the correct side of the three prong plug. I didn't figure it mattered and still had just enough power bleed into the high beam, 2 prong lamp on dim to make the filament turn orange.


Don't know why that is, but electrical isn't my thing.

Only problem is the 90 deg spades don't fit correctly into the plug now. Not a big deal, but the whole mess is a little irritating.



Thanks for the help.

[C5Phil]

Originally Posted by chalet2506

That did it. Just make sure get the ground on the correct side of the three prong plug. I didn't figure it mattered and still had just enough power bleed into the high beam, 2 prong lamp on dim to make the filament turn orange.


Don't know why that is, but electrical isn't my thing.

Only problem is the 90 deg spades don't fit correctly into the plug now. Not a big deal, but the whole mess is a little irritating.



Thanks for the help.

The ground position must have been my problem- I didn't think it mattered either- but I gave up- to soon it looks like--

[GMCJOE]

Originally Posted by davepl

In my case I just popped ALL the connections out of the headlight style connectors on the harness and redid them by following the factory color scheme. The harness has green and brown wires, as does the factory harness.

Basically one of your factory harness green wires winds up triggering a relay that powers all the green wires, which in turn connect to the headlights where the original green wires did. Same deal for the brown. I followed that basic rule and it all worked first time when I reconnected everything.

So you are saying just on the headlight side of the LMC harness you have to match up the wires to the factory harness? Nothing else required at the relay's or where you plug the power side of the factory harness into the LMC harness?

[Square_78]

Sounds like a nightmare. Hopefully LMC corrects this problem.