Anyone use the headlight relay wire harness from LMC

[Irishbleueyes]

Ordered the wire harness for GMC from LMC with the relays. Problem is the harness plug is 3 prong not 2 prong. Anyone else wire this one up?? Posted link to see the catalog page with it.
http://www.lmctruck.com/icatalog/cbe/full.aspx?Page=41

[tincan1966]

Originally Posted by Irishbleueyes

Ordered the wire harness for GMC from LMC with the relays. Problem is the harness plug is 3 prong not 2 prong. Anyone else wire this one up?? Posted link to see the catalog page with it.
http://www.lmctruck.com/icatalog/cbe/full.aspx?Page=41

Not trying to be a jerk, but which connector is 2 prong instead of 3 and what do the instructions suggest?

Not familiar with this since I do not purchase anything from LMC anymore- got tired of "some parts fit some trucks"

[Irishbleueyes]

Originally Posted by tincan1966

Not trying to be a jerk, but which connector is 2 prong instead of 3 and what do the instructions suggest?

Not familiar with this since I do not purchase anything from LMC anymore- got tired of "some parts fit some trucks"

Instructions are vague, they do mention the 4 headlight system and a 2 prong connector but the new harness has a huge 3 prong and our trucks have the 2 prong connector on the radiator bulkhead. I called them and they said to go to a shop and get it modified. Its made in Taiwan, also looks to be backwards from the battery.. It was only 30.00 bucks and came with relays.. I guess I can switch the plug out and extend the battery wires.

[Sharps40]

I just made my own harness with sockets, relays and a circuit breaker from orellies. Reused the firewall connector and eliminated the radiator bulkhead connector...ya can still pull the grill by simply unplugging from the relays.

[jbgroby]

Irish,

I have the double headlight system and have the upgrade harness. It is pretty straight out the box, they have two different one, Maybe? you got the wrong one?


PM me and I'll call you on how to wire it in.

[AnlaufJohn]

Three prong plugs are for High, Low & ground. 2 head lamp trucks like Chevrolet use 2 headlamps total.
GMC uses 4 head lamps, means 2 prongs, High/ground, Low/ground per side.
The wiring, if I were building it myself, would have 3 wires to each side, regardless of make. High, low and ground. The grounds would be paired together, attached to the frame.
I have done this upgrade for 2 of my motorcycles and my Chevy. A new wiring harness is not needed, just the relays and some wire.

[Irishbleueyes]

Originally Posted by AnlaufJohn

Three prong plugs are for High, Low & ground. 2 head lamp trucks like Chevrolet use 2 headlamps total.
GMC uses 4 head lamps, means 2 prongs, High/ground, Low/ground per side.
The wiring, if I were building it myself, would have 3 wires to each side, regardless of make. High, low and ground. The grounds would be paired together, attached to the frame.
I have done this upgrade for 2 of my motorcycles and my Chevy. A new wiring harness is not needed, just the relays and some wire.

All the wiring is correct, however its just the plug in on the radiator bulkhead, its a huge 3 prong.

[tincan1966]

I am like Sharps- I build my own. If you look thru the forums, there are several diagrams on how to build it yourself. I do mine a bit differently than most.

[Clyde65]

Can't you use the stock one and fab what you need. On my chevy there is two wires at the rad support.
Posted via Mobile Device

[jbgroby]

Ok, since I was at the same confused issue with my new halogen wiring relay harness, I decided to do a short tutorial for others like me - lack of experience.

First, buying the harness for $30.00 is cheap compared to the waste of time and cost of material needed. I'm glad for those who can build these assemblies, but for me buying the harness was just easier.

So as not to mislead, I also started with a new E-Z wiring 21 Circuit Harness.
The wires that go through the firewall to the headlight assemble are tan and green and are easily marked.

Each wire is split (left/right low beam and left/right high beam and have NO connectors on them. E-Z wire gives you two of them; you will use one during this assembly.

Picture 1 Turn your headlight assembly over and lay out you NEW Halogen relay wiring harness, you need to remember that the two red wires with BATTERY on them have to mount next to your battery location, so lay it out accordingly (please note in my picture I did it backward at first – THAT’S how I know!). Each side of the new relay harness has a black ground wire for each set of lights, make sure you have a great connection; I used a Dremel Tool sanding drum to remove paint and primer to have a direct metal to metal connection.

Plug the pre-wired harness sockets into the proper bulbs. Route your harness toward the top of your assembly and use plastic wire ties to hold in place. They should have several factory holes along the top of the headlight assembly for this purpose). When you finished getting it in place and wired tied down, you will have 2 relays, 1 male 3 prong connection and 2 red battery wire leads of the harness hanging loose.

Ok with the help of someone, carry the assembly to the front of your truck; bring the relays and red pigtail forward over the front of the assembly. Making sure not to pinch or catch them in the mounting your headlight assembly on the front of your truck. Picture 2

Work the relays, 3 prong male connector and red wires into what position you want or need. I mounted the relays on the front side of the radiator support where I could reach them (They are hidden by the radiator cowl covers)
Ok, once that is finished high five something or someone, drink a glass of your favorite beverage and let’s start on the tie into the wiring harness.
OK, the wires that will normally go directly to your factory headlight hardness (green and tan in my harness) will need to go through the radiator support grommet (may have several feet of these wires). Each single wire is split (left/right low beam and left/right high beam and have NO connectors on them. E-Z wire gives you two connectors already made into pigtails with the harness; you will use one during this assembly.

Once you feed the green and tan wire through the radiator support you will need to connect the loose wires into a female socket to them connect directly into the new relay assembly. I used the pre-wired female connector and cut and soldered that into the wires coming from firewall. Picture 4

You will have a black wire to serve as ground for the assembly. I mounted this with a self-taping screw to the radiator support as well. I have learned NOT to use the insulated butt connectors I prefer to strip and solder as well as heat shrink my connections. I find you have a better connection and (you see this as well). Takes just a few minutes longer but it will serve you well.
Once you have attached your pigtail to the OEM wiring harness, simply plug it into the new assembly and you should be ready to go and connect the new relay harness to your battery. Picture 5 and Picture 6

I hope this helps someone as I ended up calling my brother who gave me more help than the Seller of the assembly.

Any thoughts or IF someone can make this any clearer, you have my permission to do so. – Pay me with a cigar!

[jbgroby]

a few more pictures

[Irishbleueyes]

Originally Posted by jbgroby

Ok, since I was at the same confused issue with my new halogen wiring relay harness, I decided to do a short tutorial for others like me - lack of experience.

First, buying the harness for $30.00 is cheap compared to the waste of time and cost of material needed. I'm glad for those who can build these assemblies, but for me buying the harness was just easier.

So as not to mislead, I also started with a new E-Z wiring 21 Circuit Harness.
The wires that go through the firewall to the headlight assemble are tan and green and are easily marked.

Each wire is split (left/right low beam and left/right high beam and have NO connectors on them. E-Z wire gives you two of them; you will use one during this assembly.

Picture 1 Turn your headlight assembly over and lay out you NEW Halogen relay wiring harness, you need to remember that the two red wires with BATTERY on them have to mount next to your battery location, so lay it out accordingly (please note in my picture I did it backward at first – THAT’S how I know!). Each side of the new relay harness has a black ground wire for each set of lights, make sure you have a great connection; I used a Dremel Tool sanding drum to remove paint and primer to have a direct metal to metal connection.

Plug the pre-wired harness sockets into the proper bulbs. Route your harness toward the top of your assembly and use plastic wire ties to hold in place. They should have several factory holes along the top of the headlight assembly for this purpose). When you finished getting it in place and wired tied down, you will have 2 relays, 1 male 3 prong connection and 2 red battery wire leads of the harness hanging loose.

Ok with the help of someone, carry the assembly to the front of your truck; bring the relays and red pigtail forward over the front of the assembly. Making sure not to pinch or catch them in the mounting your headlight assembly on the front of your truck. Picture 2

Work the relays, 3 prong male connector and red wires into what position you want or need. I mounted the relays on the front side of the radiator support where I could reach them (They are hidden by the radiator cowl covers)
Ok, once that is finished high five something or someone, drink a glass of your favorite beverage and let’s start on the tie into the wiring harness.
OK, the wires that will normally go directly to your factory headlight hardness (green and tan in my harness) will need to go through the radiator support grommet (may have several feet of these wires). Each single wire is split (left/right low beam and left/right high beam and have NO connectors on them. E-Z wire gives you two connectors already made into pigtails with the harness; you will use one during this assembly.

Once you feed the green and tan wire through the radiator support you will need to connect the loose wires into a female socket to them connect directly into the new relay assembly. I used the pre-wired female connector and cut and soldered that into the wires coming from firewall. Picture 4

You will have a black wire to serve as ground for the assembly. I mounted this with a self-taping screw to the radiator support as well. I have learned NOT to use the insulated butt connectors I prefer to strip and solder as well as heat shrink my connections. I find you have a better connection and (you see this as well). Takes just a few minutes longer but it will serve you well.
Once you have attached your pigtail to the OEM wiring harness, simply plug it into the new assembly and you should be ready to go and connect the new relay harness to your battery. Picture 5 and Picture 6

I hope this helps someone as I ended up calling my brother who gave me more help than the Seller of the assembly.

Any thoughts or IF someone can make this any clearer, you have my permission to do so. – Pay me with a cigar!

Ok, so heres my problem - my kit didn't come with the other connector to put on in place of the 3 prong... Glad we figured that out! Thanks for all the help

[Vernski]

This is an example of lack of communication on LMC's part, they could have just as well mentioned that he needed the 2 prong pig tail and or include some directions with his purchase. Good luck Irish..Vernski

[Irishbleueyes]

Originally Posted by jbgroby

Ok, since I was at the same confused issue with my new halogen wiring relay harness, I decided to do a short tutorial for others like me - lack of experience.

First, buying the harness for $30.00 is cheap compared to the waste of time and cost of material needed. I'm glad for those who can build these assemblies, but for me buying the harness was just easier.

So as not to mislead, I also started with a new E-Z wiring 21 Circuit Harness.
The wires that go through the firewall to the headlight assemble are tan and green and are easily marked.

Each wire is split (left/right low beam and left/right high beam and have NO connectors on them. E-Z wire gives you two of them; you will use one during this assembly.

Picture 1 Turn your headlight assembly over and lay out you NEW Halogen relay wiring harness, you need to remember that the two red wires with BATTERY on them have to mount next to your battery location, so lay it out accordingly (please note in my picture I did it backward at first – THAT’S how I know!). Each side of the new relay harness has a black ground wire for each set of lights, make sure you have a great connection; I used a Dremel Tool sanding drum to remove paint and primer to have a direct metal to metal connection.

Plug the pre-wired harness sockets into the proper bulbs. Route your harness toward the top of your assembly and use plastic wire ties to hold in place. They should have several factory holes along the top of the headlight assembly for this purpose). When you finished getting it in place and wired tied down, you will have 2 relays, 1 male 3 prong connection and 2 red battery wire leads of the harness hanging loose.

Ok with the help of someone, carry the assembly to the front of your truck; bring the relays and red pigtail forward over the front of the assembly. Making sure not to pinch or catch them in the mounting your headlight assembly on the front of your truck. Picture 2

Work the relays, 3 prong male connector and red wires into what position you want or need. I mounted the relays on the front side of the radiator support where I could reach them (They are hidden by the radiator cowl covers)
Ok, once that is finished high five something or someone, drink a glass of your favorite beverage and let’s start on the tie into the wiring harness.
OK, the wires that will normally go directly to your factory headlight hardness (green and tan in my harness) will need to go through the radiator support grommet (may have several feet of these wires). Each single wire is split (left/right low beam and left/right high beam and have NO connectors on them. E-Z wire gives you two connectors already made into pigtails with the harness; you will use one during this assembly.

Once you feed the green and tan wire through the radiator support you will need to connect the loose wires into a female socket to them connect directly into the new relay assembly. I used the pre-wired female connector and cut and soldered that into the wires coming from firewall. Picture 4

You will have a black wire to serve as ground for the assembly. I mounted this with a self-taping screw to the radiator support as well. I have learned NOT to use the insulated butt connectors I prefer to strip and solder as well as heat shrink my connections. I find you have a better connection and (you see this as well). Takes just a few minutes longer but it will serve you well.
Once you have attached your pigtail to the OEM wiring harness, simply plug it into the new assembly and you should be ready to go and connect the new relay harness to your battery. Picture 5 and Picture 6

I hope this helps someone as I ended up calling my brother who gave me more help than the Seller of the assembly.

Any thoughts or IF someone can make this any clearer, you have my permission to do so. – Pay me with a cigar!

Ok, installed the grille today and with the low lights on the hi's have a slight glow and switching over to Hi's the low's have glow? Any thoughts..

[jbgroby]

no, I'll speak to my brother who is really good with electrical on cars.

[Irishbleueyes]

Originally Posted by jbgroby

no, I'll speak to my brother who is really good with electrical on cars.

Maybe the relays are bleeding over some? I took that black wire from the 3 prong plug it came with and ran it right to the neg side of the battery. Maybe its not big enough?

[jtrichard]

NO ground... High is grounding through the low and vice versa

[Irishbleueyes]

Originally Posted by jtrichard

NO ground... High is grounding through the low and vice versa

I pulled the ground from the headlight plug and went right to the frame and it didn't change. Kinda cool with the glow, which ever light is on its bright white!

[Irishbleueyes]

Heres a blog from The Corvette forum, COULD IT BE??, I can't wait to pull it apart again!

Hopefully my experience will help solve headlight bleed over experienced by others here.

This was unknown to me for some time (the problem, that is).

After I had installed a set of relays to run my headlights direct from power rather than the factory routing up to the dash cluster, then back out to the headlights, it became known to me on a trip last year that when the low beams were on, the high beams had a very minor filament glow. Clicking on the high beams, all 4 headlights were on...bright white...as it should. Clicking back to the low beams, a faint bleed over to the high beam is seen.

My electric guru neighbor, Jim Minton, persevered by cleaning the common ground for both the low and high beams, no change. Then we pulled all 4 headlights out and cleaned all the terminals on the bulbs, disassembled the tabs in the plugs on the harness and cleaned all these metal tabs as well. Reassembled and tested again...no change...still a bleed over to the high beam bulbs when on the low beam mode.

We then double checked how the DRL's were wired in, literally disassembling and carefully reassembling the wiring in...threw power on, pulled the headlight switch out, nice bright low beams and sure enough, a little bleed over to the high beam still!!

OK, we also checked the operation of the switch at the dash, disassembling the tabs on the plug from the harness at that switch, cleaning all those tabs as well. Reassembled that, threw power on and, yup, still no change.

Now we cried "Uncle"!! Called Mark at Mad Electric, who we purchased this relay kit from and explained our issue. Mark suggested using a voltmeter to see if there is any reading on the back of the ground tab of the low beam/high beam mode of the low beam connector AND he said he had seen, not too often mind you, an instance where a run of wiring harnesses had the metal tabs crossed in the plug that goes into the back of the sealed beam headlight.

He hit the nail on the head. Apparently the driver's side low beam plug had the black wire (ground) switched in the housing with the green wire (power). We decided to swap those 2 terminals and reconnected all the headlights. Nice bright low beams with NO BLEED OVER to the high beams. Clicking the dimmer switch gives a solid bright white set of beams on all 4 lights. I'm using Sylvania Halogen bulbs.

The harness is an Electric Limited harness and is probably 10+ years old. This bleed over was never noticed prior to the installation of the relays 'cause the headlights were only getting 11.5/11.6 volts. Now that they're getting a full 14 volts, that swapped terminal allowed that faint high beam glow when in the low beam mode.

Who'd a thought that was the culprit. This sure had our tails being chased!!

So, when you really get down and dirty to trace in/isolate an electric issue, ya' sometimes have to NOT assume anything.

[Irishbleueyes]

BOOOOOO YA! That was it, all the wires on the bulb connector were pushing into the wrong hole! Unreal, all that time wasted for that. Thats what I get for taking the easy route and buying a cheap harness and relays... thanks for all your thoughts and help

[seattle gmc]

Originally Posted by Irishbleueyes

BOOOOOO YA! That was it, all the wires on the bulb connector were pushing into the wrong hole! Unreal, all that time wasted for that. Thats what I get for taking the easy route and buying a cheap harness and relays... thanks for all your thoughts and help

Im having the same issue with my kit from LMC for my gmc with quad lights. A forum search led me to this thread. Could you explain a bit more how you fixed this problem.

[seattle gmc]

Originally Posted by Irishbleueyes

BOOOOOO YA! That was it, all the wires on the bulb connector were pushing into the wrong hole! Unreal, all that time wasted for that. Thats what I get for taking the easy route and buying a cheap harness and relays... thanks for all your thoughts and help

Im having the same issue with my kit from LMC for my gmc with quad lights. A forum search led me to this thread. Could you explain a bit more how you fixed this problem.

[Irishbleueyes]

Originally Posted by seattle gmc

Im having the same issue with my kit from LMC for my gmc with quad lights. A forum search led me to this thread. Could you explain a bit more how you fixed this problem.

Sure, my problem was the wires going into the plug on the harness sent from LMC. They were in the wrong location, so I switched them around till it worked. I don't remember which color goes to which tab on the headlight but it was easy to figure out. My lights are pure white and it makes a difference on the road as well. If you can't get it let me know and I will go look at where they go for you.

[seattle gmc]

Originally Posted by Irishbleueyes

Sure, my problem was the wires going into the plug on the harness sent from LMC. They were in the wrong location, so I switched them around till it worked. I don't remember which color goes to which tab on the headlight but it was easy to figure out. My lights are pure white and it makes a difference on the road as well. If you can't get it let me know and I will go look at where they go for you.

Thanks for the reply im going to look at it this weekend. Were the wires on the wrong tab on the connector that plugs into the existing wire harness, or was it one of the connectors further down the line that plug into the one of the headlights?

[Irishbleueyes]

Originally Posted by seattle gmc

Thanks for the reply im going to look at it this weekend. Were the wires on the wrong tab on the connector that plugs into the existing wire harness, or was it one of the connectors further down the line that plug into the one of the headlights?

Just the connectors at the headlight only