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'89-'91 Suburban LMC Headlight and Wiring Upgrade Write Up with Pics

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#1 OFFLINE   pma4x4


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Posted 16 February 2013 - 04:50 PM

It’ is a well know fact that a majority of factory headlights and wiring for the head lights are mediocre at best. Minimal gauge wire and multiple junctions are used to save money on the assembly line resulting in the fact that the headlamps do not get their full 12Vs they so richly deserve. Also the headlamps themselves have become dated and inefficient in projecting enough light out onto the road surface. This upgrade not only replaces the existing wiring but it also upgrades the headlamps from the traditional Lens Optic sealed beam to the newer reflector optics with a replaceable halogen bulb.

I found LMCTRUCK had the headlight upgrades that were actual glass with metal housings. They also offered a wiring harness upgrade. Now I had done this on my Jeep in the past so I knew it would have good results.


I found LMC had the headlight upgrades that were actual glass with metal housings. They also offered a wiring harness upgrade. Now I had done this on my Jeep in the past so I knew it would have good results.

Parts required
#36-0302 Low beam
#36-0303 High Beam
#36-3582 Wiring harness (This harness is required for this headlight upgrade)
Sheet metal screws
Dielectric grease

Tools required
T-15 Torx drover
13MM socket
Drill bit

if you want to make permanent connections
Wire cutter
Crimp tool
Heat shrink
Butt connectors
Wire cutters
Crimp tools

First as usual disconnect (and in this case remove the battery) before working on anything electrical.

Headlights with the wiring harness. The wiring harness has a disclaimer boldly stating "This wiring harness is NOT intended to be a replacement to the existing wiring. It is intended to plug into your existing wiring components". Uh yeah right, that's why you don't sue any of your old connectors which also means not using the old wiring. Its a simple CYA disclaimer.

NOTE: The LMC harness comes VERY WELL labeled so you cant screw it up.



Low Beam




High Beam




Start by removing the four T-15 Torx screws to remove the headlight bezel. When you are ready to remove the bezel tilt the bottom and kind of pull down. the top screw mount is a tang up under the sheet metal be careful not to break it off.




The headlight itself is held in by a metal frame and four T-15 Torx screws. This is the same on all four headlights. Remove the four screws.



TIP: Loosen the two bottoms screws about half way out and then completely remove the two screws on top. This allows you let the headlight and capture frame sit on the lower screws so you don't need a 3rd hand. The capture frame screw holes are just notched so you can pull it right off the screws when ready to swap headlights out.



A view from behind the headlights. I ran the new harness across the top of the radiator support for now.



I used this grounding point on the drivers side for the harness. The bolt was too big so I cut off the grounding rings that came with the harness and crimped on my own larger ring to fit the bolt. This bolt uses a 13mm socket.



Same ground location on the passenger side. I also had to use a new ground ring for this bolt as well. Again, use a 13mm socket on the bolt.



Harness connectors come with each of the headlights and basically what they want you to do is unplug the factory connector and just slide the tangs into the existing plug. Bare connector from new plug on left. Factory headlight connector on the right.



Take a close look and you see bare metal still in the open asking for a short.



I decided to hard wire my new connectors in. I can tell you that the wire color coding is a match for my 1991 burban. It was an easy plug and play. Tan for low beams and green for high beams.



TIP: All blue connectors are for low beam wiring and all black connectors are for high beam wiring.



Take the new connectors that came with your lights and crimp them onto the existing factory wiring harness. These will connect to your new LMC harness and will provide the on/off signal for the new relays. This after some red butt connectors and heat shrink tubing.


I use Dielectric grease on all my electrical connections. Helps keep contact and keeps moisture out. Dont spend the $4 bucks on the small permatex tube you get from an auto parts store, go to a hardware store (for me it was ACE) and spend $6 bucks on this large tube.




This seems to be a nice spot to mount the relays. I pre drilled two small holes then used two 1/4 sheet metal screws. They are clean and out of the way yet easily accessible.


End results
This was before




This was after


Final Thoughts
First off you DO NOT have to order bulbs with these headlights. Bulbs already come with them. It does not say that in the catalog so I have a spare set of bulbs.

This was a really simple project that netted some huge results. The wire gauge on the new harness is ample and plenty of length (without getting crazy) to reach even across a FS chevy engine compartment.

The connectors are so so copies of Weatherpack connectors and seem a little loose at times. Using the dielectric grease helped make a solid connection and to an extent stiffened up the connections as well.

I do wish they had used regular Bosch style relays instead of these "other" style ones.


The garage door light test does not do this upgrade any justice. the amount of light on the road is just massive compared to stock

All in all a great upgrade for a fare price.

Edited by pma4x4, 17 August 2013 - 09:33 AM.


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#2 OFFLINE   DonYukon


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Posted 16 February 2013 - 05:07 PM

YOU sir Are just FILLED with Great Write ups and Information! 


Also If you don't mind me asking whats the measurements on those lights?

Edited by DonYukon, 16 February 2013 - 05:09 PM.



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Posted 18 February 2013 - 03:31 AM

Yep, one of the most important upgrades to headlighting and its wiring................... presented perfectly.

#4 OFFLINE   Onetonsub


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Posted 21 September 2013 - 11:22 PM

excellent write up man!  thats a nice setup, I like the idea of putting more modern technology into our old trucks.


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