LMC Heavy Duty Headlight Harness Problems - The 1947 - Present Chevrolet & GMC Truck Message Board Network

SulphurDave · 07-01-2007, 09:21 PM

I tried and tried to figure this problem out on my own going on 2 weeks now. I've done some researching online and on this site and have finally windled down to nothing... as in, I'm out of ideas of what's causing my problem.

Short story long, I purchased the 4 square type euro lights with push-in style bulbs and the recommended harness to go with it. Needless to say the instructions might as well not even be printed on the back because it was lacking lots of instructions and whoever wrote the English must have flunked English Grammar 101 over there in Taiwan. Anyway... I wired everything up the only way that made sense to me and the only real questionable thing is where I plugged the harness into the existing low beam headlight harness on the passenger side. The other is where each harness was plugged into the headlights.

OK here's the problem. The first time I turned the headlights on the bottom lights (high beams) turned on and then when I clicked the high beams on the top lights came on leaving all 4 lights on. I figured this was wrong being that the top lights are the low beams. So I switch the plugs around on the headlights. That corrected it but for a while there sometimes it would work and sometimes the low beams wouldn't come on at all just the high beams. I end up running out of patience.

The next day after being fed up with it the day before, I tried it again and now the low beams were not coming on plus the parking lights were flickering and I traced the clicking noise (flickering) all the way to the headlight switch. So I bought a new headlight switch. Tried it, no low beams, still flickering, turn high beams on, they come on & flickering stops. Got fed up again.

Next day I open the door, turn the headlights on (low beams) to check and to my surprise they come on after doing nothing. I stand back puzzeled. Low beams work, high beams work & no flickering. Yay! But that was short lived. I go to crank the motor and everything trips (I have a circuit breaker for my main power). Now I'm really puzzeled. I reset the breaker, try to start the motor and it trips again. I reset it once again but this time unplugged the power to the headlight harness. Motor cranks right up. So... looks like I have multi-problems. And I'm out of ideas. Anyone?

pcmcobra · 07-01-2007, 09:24 PM

you got any pics of the wiring, did you cut any wires? Maybe you need relays, if you don't already have them.
I just put headlight relays on my truck, no problems yet.

SulphurDave · 07-01-2007, 10:59 PM

Quote:

Originally Posted by pcmcobra

you got any pics of the wiring, did you cut any wires? Maybe you need relays, if you don't already have them.
I just put headlight relays on my truck, no problems yet.

It came with relays. No I didn't cut any wires it's all plug and play. I went to RadioShack to look for some to replace them in case they were faulty but no one carries the exact ones I need. That I know of anyway. Here's a pic off of LMC's site

piecesparts · 07-01-2007, 11:57 PM

I have that very same setup sitting in my garage. I purchased it and then decided that I would not install it at this time. I have put in several wiring harnesses for the headlight upgrades in later model trucks and have had no problems with them. However if the LMC wiring setup is the same as the one that I have, the package was mostly in Oriental languages.
It sounds to me that you are not getting a good electrical signal to your relays for your headllights. I would look at the area first. Ensure that you are connecting the power source for the headlight to a good 12 volt battery source. Second look at the relay and note that it needs a good ground for the relay control circuit to work right. That means possibly putting a ground wire to the body and the power will come from the headlight switch (however the healight circuit should cover that).

What I would do is put the harness in and then connect each control relay circuit (low beam and high beam) to a good 12volt source, with jumper wires, and see if the lights work right and stay on. Once you are sure that is right, then connect it to the headlight circuit and work your way bck to the switch.

SulphurDave · 07-02-2007, 10:32 AM

Quote:

Originally Posted by piecesparts

if the LMC wiring setup is the same as the one that I have, the package was mostly in Oriental languages.

You are correct

Quote:

Originally Posted by piecesparts

Ensure that you are connecting the power source for the headlight to a good 12 volt battery source.

The main power from the harness is bolted directly to the positive battery terminal

Quote:

Originally Posted by piecesparts

Second look at the relay and note that it needs a good ground for the relay control circuit to work right.

The ground wires from the kit are bolted onto the same factory grounding wires from the original harness on the core support.

Quote:

Originally Posted by piecesparts

What I would do is put the harness in and then connect each control relay circuit (low beam and high beam) to a good 12volt source, with jumper wires, and see if the lights work right and stay on.

I did this prior to installation. Before permanently installing the harness I hooked up the lights directly to the battery to see if they worked and stayed on and they did.

Like I said, after installing the harness in the truck, I tried the lights and they all worked but it was backwards. (low beams were the bottom lights and high beams was the top lights) I then reversed the plugs on the lights themselves (made sense to me) and then they worked right but not for long. Sometimes they would come on and somemtimes they wouldn't. Clicking back and forth from low beam to high beam you can hear one relay clicking but when going to low beam I don't hear the click nor do the lights come on. Sometimes the lights will even flicker and the flicker sound comes from the headlight switch. I put a new headlight switch in and that didn't help. Meanwhile if the power source from the harness is connected to the battery the truck will not start and trips my circuit breaker. Unhook the harness from the battery, truck starts.

knightlife · 07-02-2007, 03:15 PM

honestly...its easier to just run without it...hell the instructions are in japa-friggin-ese! hell...the lights hook right up without the harness breh...if nothing else, just put the old connectors on and run with your new lights...

SulphurDave · 07-02-2007, 04:33 PM

Quote:

Originally Posted by knightlife

honestly...its easier to just run without it...hell the instructions are in japa-friggin-ese! hell...the lights hook right up without the harness breh...if nothing else, just put the old connectors on and run with your new lights...

1... the old connectors were dry rotted and most of them fell to peices as I pulled them off the old lights. 2... the main reason for doing this is because I wanted the lights to be much brighter which they are when they're working. 3... I'd rather do it the right way than settling for something else.

jb4short · 07-02-2007, 04:45 PM

the fact that the symptoms seem to change makes me believe it's a ground issue.

Restrorob · 07-02-2007, 07:55 PM

How many relays are you running in this system ?

SulphurDave · 07-02-2007, 08:54 PM

Quote:

Originally Posted by Tri-ProAutomotive

the fact that the symptoms seem to change makes me believe it's a ground issue.

I tend to make myself believe that as well but being that they are grounded on the factory bolt on the core support make me wonder. Is it possibly because both the factory harness ground wires and the heavy duty ground wires are grounded together on each side? (2 on each side)

Quote:

Originally Posted by Restrorob

How many relays are you running in this system ?

Originally none unless there's one under the dash somewhere that I don't know about. But the kit comes with 2 of them as seen in the above pic.

SulphurDave · 07-03-2007, 06:00 PM

Quote:

Originally Posted by Tri-ProAutomotive

the fact that the symptoms seem to change makes me believe it's a ground issue.

I made 2 new grounds for the h/d harness wires and left the ground wires from the original harness bolted in the factory spot. Same thing. Low beams come on and when I flick the high beams, those lights go off and high beams do not come on and the parking light bulbs flicker.

*5:36 PM Edit* Yesterday to get the truck to start I had to unplug the h/d main power harness going to the battery. If it was plugged in and I tried to start it, it tripped my circuit breaker everytime. After relocating the ground wires like I just mentioned above, I unplugged the harness to see if the truck would start like yesterday. It tripped. I did this over and over a few times having to keep resetting the breaker. Then I plugged the h/d main power harness back in just to see how my luck was and it cranks up which is totally opposite of what was happening yesterday. Oh yea.. and the high beams still don't come on. I'm drenched with sweat, tense from wanting to throw my tools across the yard and my patience has run out on this little headlight project.

Roper · 07-04-2007, 10:09 AM

Did your old lights work good before you put on the LMC stuff?
Man I wish I could help you.
Okay this is probable super dumb but is it possible your high/low beam selecter thats on the floor? Sometimes when they get bad they can make your lights do wierd things although I never heard tell of one doing what your lights are doing.

SulphurDave · 07-06-2007, 03:02 PM

Can anyone else shed some light on the subject?

**Thealien** · 07-06-2007, 05:28 PM

I would check for voltage with a meter at each relay. is the power going to the relay? When the relay is powered does the relay coill actually get voltage? If so is voltage leaving the relay?

IMHO with what you describe there is no power (for the lights) going to the second relay.

It does look difficult to test those relays but you could unplug the relay and check at the plug.

Good luck.

Since one relay seems to be working I would check for power on that plug with the lights off and on, on high beam the other relay should have power in all the same places.

SulphurDave · 07-06-2007, 08:20 PM

Quote:

Originally Posted by Thealien

I would check for voltage with a meter at each relay. is the power going to the relay? When the relay is powered does the relay coill actually get voltage? If so is voltage leaving the relay?

IMHO with what you describe there is no power (for the lights) going to the second relay.

It does look difficult to test those relays but you could unplug the relay and check at the plug.

Good luck.

Since one relay seems to be working I would check for power on that plug with the lights off and on, on high beam the other relay should have power in all the same places.

Yea I'm waiting on one of my buddies to come over with his tester. We're gonna check all that out and see what's happening.

84_chevrolet · 09-13-2007, 10:10 AM

Hey man did u ever get everything to work right? i installed one of lmc harnesses last night and it worked great for me. How do u like the euro headlights are they worth the money?

SulphurDave · 09-13-2007, 10:01 PM

Quote:

Originally Posted by 84_chevrolet

Hey man did u ever get everything to work right? i installed one of lmc harnesses last night and it worked great for me. How do u like the euro headlights are they worth the money?

Honestly I have no idea what fixed it because I've messed with so much in between and other things not really related to this problem that one day they miraculously started working. Can't explain it though. That's not to say they will work next week though. I think that if you maintained the sealed beams but juiced them up with the extra voltage from the harness the light output would be comparable to the "bulbs" that came with the euro lights from LMC. You can always upgrade the bulbs to a brighter blue'er hue like the h.i.d. look-a-like bulbs the imports use if you wanted that.

82GMC4X4 · 09-14-2007, 05:05 AM

I know I am jumping in here a little late, I am glad you god your lights working, I hate wiring crap like that, anywho. I was reading through all of this and somewhere in there you said that when you hit your high beams on, all four lights stayed on and you thought that was wrong, on my truck, if I turn on the high beams, all of them come on as well. Maybe I just read it wrong.

84C10Chance · 07-25-2012, 01:58 PM

Thread Revive!! lol. I typed in something about the harness and this popped up.

Here was my issue. I bought this harness to hopefully fix the issue im having.

Alright, So i bought some 6k HIDs for the 84 and when plugged all up they only come on with the brights on. So i just unplugged the normals and left the brights plugged in. Well sometimes the bulb flickers and everything. Had them tested and they work just fine. The guy told me on those these old vehicles the wiring wasnt all that great and that i should just hook the lights up to some relays and straight to the battery. Well I was looking through the LMC catalog and notice they had a harness that does just exactly what the guy told me. So i bought the harness and it arrived today. Question is how does this work with turning the headlights on and off if its going straight to the battery?

Also, How in the hell do i get my reverse lights to come on when putting it reverse?? Ive tried adjusting it, But i see now way in adjusting the lever??

84C10Chance · 07-25-2012, 06:37 PM

Also the plug that suppose to go to the harness. Do you just simply plug it into the high plug? Or what??

WarBeard · 07-25-2012, 07:46 PM

piecesparts · 07-25-2012, 10:36 PM

The trigger for the relays is the headlight circuit from the factory installed wiring. There should be a plug on the harness that fits either the low beam or the high beam headlight bulb plug or both of them. When you turn the headlights on, the relay will close and the power from the battery will go straight to the HID bulbs.

84C10Chance · 07-25-2012, 11:14 PM

Well ive got the harness hooked up. And im getting the same problem as i was before with the HIDs. Heres a video to show what im talking about.

http://www.youtube.com/watch?v=bGEaP...ature=youtu.be

84C10Chance · 07-25-2012, 11:15 PM

Well ive got the harness hooked up. And im getting the same problem as i was before with the HIDs. Heres a video to show what im talking about.

http://www.youtube.com/watch?v=bGEaP...ature=youtu.be

beamn7 · 07-26-2012, 03:33 AM

I got one of these harnesses and had to re-pin it as I was having similar issues. Turns out the plug for the harness that plugs into the low beam plug on the truck was pinned backwards as was all 4 of the headlight connectors. By the time I was done I could have just built my own (as I had originally planned)...oh well...

Incidentally, my 85 has all 4 headlights come on as well with the high beams on (both before and after this harness install) and by looking at the GM schematics, that is the way it is supposed to be. GM manual from 85 also shows low beams on top, high beams on bottom but, I've seen them both ways so, depends on who was working that day!

07-01-2007, 09:21 PM	#1
SulphurDave Registered User Join Date: Sep 2006 Location: Sulphur, LA Posts: 259	LMC Heavy Duty Headlight Harness Problems I tried and tried to figure this problem out on my own going on 2 weeks now. I've done some researching online and on this site and have finally windled down to nothing... as in, I'm out of ideas of what's causing my problem. Short story long, I purchased the 4 square type euro lights with push-in style bulbs and the recommended harness to go with it. Needless to say the instructions might as well not even be printed on the back because it was lacking lots of instructions and whoever wrote the English must have flunked English Grammar 101 over there in Taiwan. Anyway... I wired everything up the only way that made sense to me and the only real questionable thing is where I plugged the harness into the existing low beam headlight harness on the passenger side. The other is where each harness was plugged into the headlights. OK here's the problem. The first time I turned the headlights on the bottom lights (high beams) turned on and then when I clicked the high beams on the top lights came on leaving all 4 lights on. I figured this was wrong being that the top lights are the low beams. So I switch the plugs around on the headlights. That corrected it but for a while there sometimes it would work and sometimes the low beams wouldn't come on at all just the high beams. I end up running out of patience. The next day after being fed up with it the day before, I tried it again and now the low beams were not coming on plus the parking lights were flickering and I traced the clicking noise (flickering) all the way to the headlight switch. So I bought a new headlight switch. Tried it, no low beams, still flickering, turn high beams on, they come on & flickering stops. Got fed up again. Next day I open the door, turn the headlights on (low beams) to check and to my surprise they come on after doing nothing. I stand back puzzeled. Low beams work, high beams work & no flickering. Yay! But that was short lived. I go to crank the motor and everything trips (I have a circuit breaker for my main power). Now I'm really puzzeled. I reset the breaker, try to start the motor and it trips again. I reset it once again but this time unplugged the power to the headlight harness. Motor cranks right up. So... looks like I have multi-problems. And I'm out of ideas. Anyone? __________________ My 84 C10 build... http://67-72chevytrucks.com/vboard/s...d.php?t=216158

07-01-2007, 09:24 PM	#2
pcmcobra Registered User Join Date: Aug 2006 Location: Florida Posts: 1,684	Re: LMC Heavy Duty Headlight Harness Problems you got any pics of the wiring, did you cut any wires? Maybe you need relays, if you don't already have them. I just put headlight relays on my truck, no problems yet. __________________ 1986 C10 SWB 6.0/6l90e Miami...Flee it like a native

07-01-2007, 11:57 PM	#4
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: LMC Heavy Duty Headlight Harness Problems I have that very same setup sitting in my garage. I purchased it and then decided that I would not install it at this time. I have put in several wiring harnesses for the headlight upgrades in later model trucks and have had no problems with them. However if the LMC wiring setup is the same as the one that I have, the package was mostly in Oriental languages. It sounds to me that you are not getting a good electrical signal to your relays for your headllights. I would look at the area first. Ensure that you are connecting the power source for the headlight to a good 12 volt battery source. Second look at the relay and note that it needs a good ground for the relay control circuit to work right. That means possibly putting a ground wire to the body and the power will come from the headlight switch (however the healight circuit should cover that). What I would do is put the harness in and then connect each control relay circuit (low beam and high beam) to a good 12volt source, with jumper wires, and see if the lights work right and stay on. Once you are sure that is right, then connect it to the headlight circuit and work your way bck to the switch.

07-02-2007, 03:15 PM	#6
knightlife Dark Heart Motorsports Join Date: Apr 2007 Location: 29404 DKFX Posts: 683	Re: LMC Heavy Duty Headlight Harness Problems honestly...its easier to just run without it...hell the instructions are in japa-friggin-ese! hell...the lights hook right up without the harness breh...if nothing else, just put the old connectors on and run with your new lights... __________________ How Deep Can YOU Bleed..? 1985 Chevy Blazer K5- 6.2 N/A, 400 turbo trans CUCV, 12v converted... a new chapter 2005 GMC Sierra Crew Cab 6.0 powwwaa!!! custom jumpseat install w/ captain seats, Hypertech tuner, MSD Blaster Coils, CB and twin antenna's, all electric interior, touch screen in dash. custom center console, with jump seat replacing original console. 1500 HD!

07-02-2007, 04:45 PM	#8
jb4short Damn Yankee Join Date: Feb 2007 Location: Lynchburg, VA Posts: 2,261	Re: LMC Heavy Duty Headlight Harness Problems the fact that the symptoms seem to change makes me believe it's a ground issue.

07-02-2007, 07:55 PM	#9
Restrorob The One And Only !!! Join Date: Jan 2007 Location: Hole in the woods Florida Posts: 4,567	Re: LMC Heavy Duty Headlight Harness Problems How many relays are you running in this system ? __________________ 93 Jeep XJ 88 Buick La Sabra Toys; 88 TA-GTA in the works.... 97 GMC Ext. Cab 502 Crate 5 Spd......Sucks Gas But Haulz Azz ! The primary function of an Engineer is to make it difficult for the Fabricator and impossible for the Mechanic. *"Why go out preserved when you can go out beat up, worn out, sliding in sideways screaming, Holy Sh!t What A Ride" !!!*

07-04-2007, 10:09 AM	#12
Roper Registered User Join Date: Feb 2005 Location: Alberta Posts: 248	Re: LMC Heavy Duty Headlight Harness Problems Did your old lights work good before you put on the LMC stuff? Man I wish I could help you. Okay this is probable super dumb but is it possible your high/low beam selecter thats on the floor? Sometimes when they get bad they can make your lights do wierd things although I never heard tell of one doing what your lights are doing.

07-06-2007, 03:02 PM	#13
SulphurDave Registered User Join Date: Sep 2006 Location: Sulphur, LA Posts: 259	Re: LMC Heavy Duty Headlight Harness Problems Can anyone else shed some light on the subject? __________________ My 84 C10 build... http://67-72chevytrucks.com/vboard/s...d.php?t=216158

07-06-2007, 05:28 PM	#14
Thealien Senior Member Join Date: Jun 2007 Location: Pine Ridge Florida Posts: 4,134	Re: LMC Heavy Duty Headlight Harness Problems I would check for voltage with a meter at each relay. is the power going to the relay? When the relay is powered does the relay coill actually get voltage? If so is voltage leaving the relay? IMHO with what you describe there is no power (for the lights) going to the second relay. It does look difficult to test those relays but you could unplug the relay and check at the plug. Good luck. Since one relay seems to be working I would check for power on that plug with the lights off and on, on high beam the other relay should have power in all the same places.

09-13-2007, 10:10 AM	#16
84_chevrolet Truck CRAZY! Join Date: Mar 2004 Location: douglas Posts: 81	Re: LMC Heavy Duty Headlight Harness Problems Hey man did u ever get everything to work right? i installed one of lmc harnesses last night and it worked great for me. How do u like the euro headlights are they worth the money? __________________ 84 Chevrolet stepside, 350 with .60 over pistons, aluminum zr1 heads, doug herbert .500 lift cam, 1.6 roller rockers, elderbrock intake with a 600 holley carb, mated to a 700r4, 208t-case and 4-11 gears,33 goodyear wrangler mtrs

09-14-2007, 05:05 AM	#18
82GMC4X4 Registered User Join Date: Jul 2007 Location: Regina, Sk, Canada Posts: 10	Re: LMC Heavy Duty Headlight Harness Problems I know I am jumping in here a little late, I am glad you god your lights working, I hate wiring crap like that, anywho. I was reading through all of this and somewhere in there you said that when you hit your high beams on, all four lights stayed on and you thought that was wrong, on my truck, if I turn on the high beams, all of them come on as well. Maybe I just read it wrong.

07-25-2012, 01:58 PM	#19
84C10Chance Registered User Join Date: May 2009 Location: Saginaw, Texas Posts: 20	Re: LMC Heavy Duty Headlight Harness Problems Thread Revive!! lol. I typed in something about the harness and this popped up. Here was my issue. I bought this harness to hopefully fix the issue im having. Alright, So i bought some 6k HIDs for the 84 and when plugged all up they only come on with the brights on. So i just unplugged the normals and left the brights plugged in. Well sometimes the bulb flickers and everything. Had them tested and they work just fine. The guy told me on those these old vehicles the wiring wasnt all that great and that i should just hook the lights up to some relays and straight to the battery. Well I was looking through the LMC catalog and notice they had a harness that does just exactly what the guy told me. So i bought the harness and it arrived today. Question is how does this work with turning the headlights on and off if its going straight to the battery? Also, How in the hell do i get my reverse lights to come on when putting it reverse?? Ive tried adjusting it, But i see now way in adjusting the lever??

07-25-2012, 06:37 PM	#20
84C10Chance Registered User Join Date: May 2009 Location: Saginaw, Texas Posts: 20	Re: LMC Heavy Duty Headlight Harness Problems Also the plug that suppose to go to the harness. Do you just simply plug it into the high plug? Or what??

07-25-2012, 07:46 PM	#21
WarBeard Registered User Join Date: Jul 2008 Location: Show low,az Posts: 808	Re: LMC Heavy Duty Headlight Harness Problems Attached Images __________________ 1978 C10 Silverado Big 10 350/350.. play toy 1990 V1500 Suburban 350/700r4..Daily driver 1987 K10 Silverado 383/400.. Wife's rig WRECKED! 1989 V2500 Suburban 350/400.. SOLD! 1974 C10 Custom10 LWB 350/350.. SOLD! 1974 C10 Custom10 SWB 350/400.. SOLD! 1999 Silverado Z71 LS1.. Wife's rig WRECKED! On the hunt for a new project....... I'm a Chevy guy.....I'm just not a "NEW" Chevy guy.

07-25-2012, 10:36 PM	#22
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: LMC Heavy Duty Headlight Harness Problems The trigger for the relays is the headlight circuit from the factory installed wiring. There should be a plug on the harness that fits either the low beam or the high beam headlight bulb plug or both of them. When you turn the headlights on, the relay will close and the power from the battery will go straight to the HID bulbs. __________________ Frank



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07-25-2012, 11:14 PM	#23
84C10Chance Registered User Join Date: May 2009 Location: Saginaw, Texas Posts: 20	Re: LMC Heavy Duty Headlight Harness Problems Well ive got the harness hooked up. And im getting the same problem as i was before with the HIDs. Heres a video to show what im talking about. http://www.youtube.com/watch?v=bGEaP...ature=youtu.be

07-25-2012, 11:15 PM	#24
84C10Chance Registered User Join Date: May 2009 Location: Saginaw, Texas Posts: 20	Re: LMC Heavy Duty Headlight Harness Problems Well ive got the harness hooked up. And im getting the same problem as i was before with the HIDs. Heres a video to show what im talking about. http://www.youtube.com/watch?v=bGEaP...ature=youtu.be

07-26-2012, 03:33 AM	#25
beamn7 Registered User Join Date: Oct 2011 Location: Wildomar, CA Posts: 466	Re: LMC Heavy Duty Headlight Harness Problems I got one of these harnesses and had to re-pin it as I was having similar issues. Turns out the plug for the harness that plugs into the low beam plug on the truck was pinned backwards as was all 4 of the headlight connectors. By the time I was done I could have just built my own (as I had originally planned)...oh well... Incidentally, my 85 has all 4 headlights come on as well with the high beams on (both before and after this harness install) and by looking at the GM schematics, that is the way it is supposed to be. GM manual from 85 also shows low beams on top, high beams on bottom but, I've seen them both ways so, depends on who was working that day!

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