New Headlight Harness Update Help ?!?!?

[Norwester]

So! I decided to upgrade the headlight harness on my '86 with single headlights as they looked pretty dim to me. Now, I'm not much of a mechanic and the electrical system is pretty much voodoo to me but the kit from LMC looked pretty easy and emphasized no cutting or splicing.

The kit came and I spent a few minutes at my bench, adding some wire loom to dress it up a bit. Bought some new shiny stainless sheet metal screws for the two ground points and for the relays.

Mounted the relays near the radiator, tacked down the grounds, swapped the kit plugs for the truck's plugs, attached the two power wires to the battery, and hit the headlight switch.......NO LIGHTS! Well, I have parking lights but I assume they are on another circuit.

Now I am 99.9999% sure I mounted the kit correctly as it was very straight forward and the skimpy instructions were clear enough.

I reattached the truck's harness just to make sure I didn't blow a fuse and the lights worked fine. Now I'm not sure how to diagnose the problem.

Do folks have problems with the LMC kit being wired improperly?

Any ideas how to diagnose?

As always, thanks in advance

 

[HotRodPC]

I'm not familiar with this LMC Harness you speak of, but I've changed your thread title to relate to your need and hopefully that will bring some help in.

I'm curious though, you mention headlight harness upgrade. How is this an upgrade or is it actually just a harness replacement of the OEM harness?

Have you seen any of the headlight relay wiring diagrams where we actually do upgrade the OEM headlight wiring which puts more voltage to the headlights for brighter lights? It's actually not adding any voltage to the system, but the way it's wired, you're not getting any voltage loss at the headlights.

 

[Norwester]

I'm not familiar with this LMC Harness you speak of, but I've changed your thread title to relate to your need and hopefully that will bring some help in.

I'm curious though, you mention headlight harness upgrade. How is this an upgrade or is it actually just a harness replacement of the OEM harness?

Have you seen any of the headlight relay wiring diagrams where we actually do upgrade the OEM headlight wiring which puts more voltage to the headlights for brighter lights? It's actually not adding any voltage to the system, but the way it's wired, you're not getting any voltage loss at the headlights.

Thanks for the title change...more appropriate.

The harness kit from LMC is supposed to do what you suggest...cut down on the voltage loss from the switch. I know that some folks wire in relays and run power directly from the battery using parts they buy at the parts store. The kit from LMC includes all that and is preassembled for easy installation.

Well, it WAS easy.....just didn't work.

 

[HotRodPC]

OK, so it actually is an upgrade kit and does use relays. So when you say it didn't work, do you mean it didn't make your headlights brighter, or they don't work at all now?

EDIT: My bad, I missed a paragraph above. Now I see the part about relays and no headlights coming on.

 

[Fastereddie]

Do you have a volt meter handy?

 

[Norwester]

Do you have a volt meter handy?

I do....just not sure what to check

 

[Norwester]

This is what I checked and what I found:

I put my test light on both headlight plugs from the truck...all good

Put my light on the connector that connects the new harness to the battery...all good

Each relay has 4 spade connections. On one relay, two of the spades lit up. On the other relay, one spade lit up. I'm assuming the two relays are for low/high beams. I didn't know how to interpret the results.

 

[Fastereddie]

Your relay should have four terminals. One goes to battery,(30) one to headlight,(87)one to switched power,(86)and one to ground,(85)
The switched power one should be connected to your existing headlight harness that has 12vdc when you turn them on. Hope that helps.

 

[Fastereddie]

Maybe the headlights aren't getting a ground. Not sure without seeing the harness.

 

[Norwester]

Maybe the headlights aren't getting a ground. Not sure without seeing the harness.

I appreciate the feedback. While I think my grounds are ok, it will be the first thing I check.

I've read on other forums about people buying that kit and discovering that wires were reversed in the harness. Another thing to check.

I called LMC and I think they are going to send another harness. We'll see and if they do, it might be interesting to compare the wiring in both.

Thanks again

 

[chengny]

Pull the connectors off both sealed beams. Turn on the headlights at the main switch. Toggle to low beams. Use your meter to see if there is power at any of the LMC leads where they connect to the lamps.

If you find that you get power at one of the female connectors in each plug, mark it someway that indicates low beams.

Toggle the dip switch to highs and check for voltage at the headlight connectors again. With any luck there will be power - and on a different terminal clip. That would be the high beam circuit.

If you get voltage on two different leads - and it moves with the dip switch - the problem is either a grounding issue or incorrect connections at the headlights.

Next, look at the relationship between the female terminals in the plug and the male terminals at the back of the sealed beam.

You should have the 2B1 type headlights - unless they've modified. The 2B1 style is a standard Delco 6052 sealed beam - or an H6054 if you use halogens. Regardless, the high/low beam leads in the LMC harness must be connected to the lamp terminals as shown:

You must be registered for see images attach

If the leads don't correspond to the terminals correctly, rearrange them either by cutting/splicing the leads or removing the female terminals from the connector housings and installing them in the right slots.

If that wasn't the problem, or it did not help, check the black wires at each plug for continuity to ground.

 

[Norwester]

Pull the connectors off both sealed beams. Turn on the headlights at the main switch. Toggle to low beams. Use your meter to see if there is power at any of the LMC leads where they connect to the lamps.

If you find that you get power at one of the female connectors in each plug, mark it someway that indicates low beams.

Toggle the dip switch to highs and check for voltage at the headlight connectors again. With any luck there will be power - and on a different terminal clip. That would be the high beam circuit.

If you get voltage on two different leads - and it moves with the dip switch - the problem is either a grounding issue or incorrect connections at the headlights.

Next, look at the relationship between the female terminals in the plug and the male terminals at the back of the sealed beam.

You should have the 2B1 type headlights - unless they've modified. The 2B1 style is a standard Delco 6052 sealed beam - or an H6054 if you use halogens. Regardless, the high/low beam leads in the LMC harness must be connected to the lamp terminals as shown:

You must be registered for see images attach

If the leads don't correspond to the terminals correctly, rearrange them either by cutting/splicing the leads or removing the female terminals from the connector housings and installing them in the right slots.

If that wasn't the problem, or it did not help, check the black wires at each plug for continuity to ground.

I replied to your post this morning....must have done something wrong. In any case, thank you for the information. That gives me a good list of things to look for. I'll let you folks know if and when I figure it out.

 

[Norwester]

Ok....did some testing with a test light, assuming that is ok.

First I checked my new harness grounds by touching the battery positive and probing the grounding points on the new harness. Everything seemed fine.

I then probed the truck's headlight sockets with the low beams and then the high beams on. Everything matched the terminals picture that chengyny provided.

I attached the new harness to the passenger side harness that goes to the truck. Probing, I found the negative was fine but I couldn't get any power out of the low beam or high beam terminals. Switching to high beams, I did it again and once more couldn't find any power.

Does this mean that my high and low beam terminals need to be switched? I dug around a little in the terminals but couldn't seem to be able to dislodge the spades. Maybe there's a trick to it?

I really don't want to cut and splice unless I have to....is there anymore testing I can do to be sure of what the problem is?

 

[yevgenievich]

Check to make sure that one of the terminals foreach relay has constant 12v( should be labeled 30).
I have one of lmc headlight harness sitting on the shelf. Don't know how i missed the type of relays they use before buying it, but did not like it overall.

 

[Norwester]

Victory is mine! I finally decided that some wires in the LMS harness must be reversed so I got into the male plug in the harness that plugs into the truck's harness. I switched the low and high beam terminals, and everything worked fine.

I routed the new harness under the radiator and found it to be about 18" too short so I spliced in some wiring.....yes, I soldered and heat shrunk!

I do thank those of you that offered comments.