Headlight Harness Help - Connecting to Existing

[Mthumphrey]

Hey guys... Not much of a electrical specialist here. Maybe you can help. I have a 66 C10 and purchased a headlight harness from LMC. Sounds great, but it came with a 3 prong connector (connects to original harness). The original is a female 2 prong connector (see picture attached). A few questions here.

1. What is the 3rd prong for?
2. Will this at all work if I were to splice it?
3. Or should I just return it? LMC was useless in helping here.

Thanks!
Michael

[DPowers]

I think you got the wrong part.
Give these guys a try.

http://www.wiringharness.com/

[1963c-10]

I'd contact the supplier. Should be a two prong as mentioned and as seen on the original.

[Figuarus]

So i've got to ask...

Are you looking to stick to something factory original, or to update the harness?

If you are ok with modifying the harness a bit, just use the high/low beam wires from the dimmer switch, and wire them to a set of relays.

[theastronaut]

It looks like the three prong connector will plug into one of the old headlight sockets.

[Mthumphrey]

Thanks guys!

Figuarus: I am having some issues with dimming and also high beams only working. I have cleaned all of the wires and replaced the dimmer. I thought it might be easiest just to replace the headlight harness... This one has the built in relays that run directly to the battery as you show. I thought this new harness would fix it. I was thinking of just changing the headlight harness only.

I had thought to just cut the 3 prong off of the new harness, but there are 3 wires in it. There would be one odd wire out. Just not sure what that odd wire may do... It has 1 brown, 1 white and 1 blue/white wire. The brown and white wires run directly to the relays (there are 2 and one runs to each of them). There are additional connections made underneath the sheathing because the 1 blue/ white wire splits and runs to both relays. Each headlight has 1 blue and 1 yellow wire running from it to separate relays (2 yellows to one and 2 solid blues to the other). Of course, there is a black ground with each headlight.

All of this matches your drawing and is what makes sense to me, but I don't know what to do with the other wire... I expect it is the blue/ white stripe wire that has me stumped. Would I need to run a 3rd wire from this connector to the headlight switch?

[Figuarus]

Originally Posted by Mthumphrey

I thought this new harness would fix it. I was thinking of just changing the headlight harness only.

Humphrey,

That's why I just made a new harness. I used a set of 3 prong pigtail connectors from O'reilly's, and two relays.

The rest is just wiring it all together according to the relay diagram I posted above.

If you do it right, it can be a pretty clean install. Use a set of these relays http://www.amazon.com/gp/product/B007M47SW0/ref=ox...
The nice thing about these is that you get a 5 pack, and they come with the connectors to make changing them easy.

[BR3W CITY]

Originally Posted by Figuarus

Humphrey,

That's why I just made a new harness. I used a set of 3 prong pigtail connectors from O'reilly's, and two relays.

The rest is just wiring it all together according to the relay diagram I posted above.

I ended up doing pretty much the same. I ditched the old horn relay and seperated the high, low, and horn to their own relays. We actually twisted wire pairs and remade the front harness ourselves, keeping the firewall connector stock (just repinned).

[theastronaut]

The new three wire plug most likely plugs into one of your existing headlight pigtails. It will use the low beam wire to turn on the low beam relay, the high beam wire to turn on the high beam relay, and probably ground both relays with the factory ground wire. Then you hook up the new power (and maybe ground) wires to the battery. If you are having trouble switching from high to low without the harness then the harness won't fix the existing problems.

[franken]

The existing connector on the left in the pic isn't for a headlight. The seemingly new male connector on the left plugs into a 3 socket female headlight plug that normally connects to a headlight.
66 Chevy has a 2 headlight setup, so they have 3 spade connectors sticking out of them, just like your new harness.

[Mthumphrey]

So, your saying that I leave my existing headlight harness and plug this 3 pronger into one of the existing connectors that normally plugs into the headlight? Why would they do that? Then I will have 2 sets of wires running in the grill?

[theastronaut]

The whole point of a relay harness is to take power for the lights straight from the battery using heavier gauge wire for minimal voltage drop at the bulbs. The part that hooks up to your existing harness only functions to power the relays. So if your current headlight wiring isn't functioning then the relay harness won't fix existing problems, and won't function properly until the original headlight wiring is working.

[Mthumphrey]

I understand about not fixing my original issues... I will still have them, but I don't understand why it would be wired in that manner. The whole idea was to replace the old wiring and have direct power from the battery... It should help with the dimming issue.

[chevy_mike]

The upgraded headlight harness is designed to plug into the headlight pigtail connector, so you don't have to modify any factory wiring. The pigtail on the left is the one that comes from the interior harness to the front core support. It then has another harness that goes to the headlights. Since the factory headlights ground through the core support harness, the one coming from the interior doesn't need the extra wire.

If you want to remove the factory headlight core harness, you will need to figure out which of the two wires in the left plug is for high and low beams. You would splice them into your new harness, for the appropriate circuit. The extra wire would be a ground wire, which you can screw to the core support.

Hope that makes sense.

[jtrichard]

Really need pics of ALL connectors on your new wiring because with a relay system you need 4 connections ...#1 batt power..#2 ground....#3low beam...#4 high beam ONLY see 3 in your pic ..... Sorry to say that with ONLY this one pic this is nothing more than a guessing game........ I am sure you would like to know just what you have and how to hook it up

[Mthumphrey]

Maybe I will try making my own. Thanks guys!!!