Headlight harness for 1963 GMC truck
 

Hope all are well. I am needing to replace the headlight harness wiring for 1963 GMC truck. I bought the headlight harness that LMC has for that year of truck and they say works for both GMC and Chevy. But the harness from LMC has the red wire going to starter by itself and a single black wire by itself and then a double connection with two wires on it. On the 1963 GMC the light harness that is on truck has a three wire connection going to starter that connects with another 3 wire harness near the air filter that then goes to the starter. Does anyone know where to buy a light harness that will fit the 1963 GMC truck with the 3-wire connection set up? Or has anyone retro fitted the LMC light harness so they it connects into the existing 3wire connection that goes down to starter? Here is a picture of the LMC type headlight harness with connection highlighted in yellow that talking about above. Thanks.

Kevin

Re: Headlight harness for 1963 GMC truck
 

Here is snap pic of 3 wire plug from 1963 GMC wiring diagram that I am looking for on headlight harness.

Re: Headlight harness for 1963 GMC truck
 

Rex, you all all mixed up and the internet has you further mixed up. There is NO 3wire connector that you show on that home made wiring diagram from somewhere. There are NO starter wires in a headlight harness.

If you will post the LMC harness part number and can answer some questions, I will help you get your truck wired. Post the instructions you received for the Harness. Where did you get the picture of the harness and where did you get the wiring diagram picture?

If I see you are not monitoring this post regularly, I will not help you.

Re: Headlight harness for 1963 GMC truck
 

Ken,
Thanks for your reply. The LMC part number for the Heavy Duty headlight harness for a 4-bulb GMC headlights is 36-3581. I got the wiring diagram from 6066 GMC club forum. The picture of headlight harness came from a picture American Autowire had on their website. I was looking at their site to see if they had harness and they had that pic that matched what I got from LMC, so I just used that to snap pic. The original wiring that is on the truck now, has the connector at the firewall, that runs the high and low beam wire to the grille and then also has the 3 wires that run over to the air filter that connects to the 3 wire connector. I can send pictures of that if would help. Thank you!


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Re: Headlight harness for 1963 GMC truck
 

I have a suggestion if you want/need to rewire your GMC headlights - it's not a plug and play project but this will give you a much brighter lights that your truck came from the factory with. First we ALL HERE need to know what is wrong with your wiring harness - if the front wiring to your the lights are good I would pick a spot between your floor dimmer switch and the good existing headlight harness and install a HEADLIGHT RELAY that provides full voltage to the bulbs. Factory systems run all your voltage current thru the headlight switch on the dash to power your lights - if your upgrade your bulbs to any thing other than original sealed beams you stress the contacts in the little switch. Be much easier upgrading your existing harness that getting an all ready cluster mess not designed for the GMC.:thumbsup:

Re: Headlight harness for 1963 GMC truck
 

Lizzie,
I agree. And that is what I am doing with the the headlight is installing the heavy duty headlight from LMC part # 36-3581. Ken, apologies on my reply back to you, I gave you the heavy duty headlight part number instead of the headlight harness part number. The LMC headlight harness I purchased from LMC is Front Lamp Harness part # 36-3160.
Lizzie, to your question, what am I trying to do. I have installed heavy duty headlight relay and now trying to get headlights lighting up. I am getting voltage out of the dimmer switch on low and high beam wire. I am loosing that voltage between there and the connector at grille for the headlights. I don’t see a break in the wire or anything obvious. The wire is old, so wanted to put new wire from firewall to connector at grille. And that is why I am trying to replace the light harness on hood side at firewall. Good question Lizzie. Thanks.


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Re: Headlight harness for 1963 GMC truck
 

I guess you want to wire in the new headlight harness. Is that right? Are there any instructions? If so, can you post? If not, can you post pics of the actual harness you have, showing each wire and connector. Spread out, not a stock web pic.

I am a bit confused still. Did you buy two harnesses? If so, why? You do not need heavy duty. You do not need relays. Slow down. You are getting carried away and spending money for items you don't need. You can buy a whole harness for $200. For the whole truck. So what did you already buy? What headlights are you installing? LED, Halogen, sealed beam...... Do you have an alternator or a generator? Are either of those new?

I agree with Lizzie 100% except for the relays. So I guess 99%. He is knowledgeable. We can differ by 1%.

The diagram you found is full of errors. Someone took a Chevy diagram and tried to turn it into a GMC diagram by looking at the official GMC diagram and using a cad program. Also, I do not think the harnesses you bought are actually for Chevy or GMC. I think they are Chevy. These two things are what is going to confuse you. If you wish, I will help you thru this mess if you answer my questions above.

Re: Headlight harness for 1963 GMC truck
 

Ken,
Thanks for your reply and questions. Here are some details and answers to your questions.

- main goal: get headlights burning

- I have read on 6066 forums advantages to headlight relay system, so have installed that.

- pictures of headlight harnessed are attached to this reply.

- I bought 1 headlight harness and 1 relay wire kit for headlights. I looked at headlight harness and it actually came from American Autowire instead of LMC, like I had originally said. Pics of headlight harness and headlight relay kit attached.

- Halogen headlights are installed

- generator is on truck and it looks like it has been on there a while. Truck runs and is pushing correct voltage back to battery.

Thanks Ken for the help. And let me know if you need more details on something. The Attachment 8937


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Re: Headlight harness for 1963 GMC truck
 

Pics attached

Re: Headlight harness for 1963 GMC truck
 

I have voltage coming out of the dimmer on the low and high wires. And then here at grille, pic attached, I do not have voltage.

Re: Headlight harness for 1963 GMC truck
 

OK, so you have purchased TWO headlight harnesses. Nothing is labeled "Relay Kit". Which one have you installed? What, if anything, have you "added" to the existing original wiring? Is some of the existing wiring in place or torn out?

I realize you don't have voltage somewhere. We will get to that.

1. You have two firewall connectors. Left side is a 9 pin. This is actually a separate 3 pin and a 6 pin plugged into the bulkhead connector 9 pin. Right?
Right side is a 6 pin. Right?
2. You have one 2 pin headlight feed connector mounted on radiator support, left side. That is the one in your pic that you say no voltage there, right?
3. You should have a 1 pin horn connector, a 2 pin horn relay connector and oil and temp sender 1 pin "connectors". Yes?
4. Have you done any wiring inside cab?
5. Explain exactly how you determined no voltage, and exactly where on truck. With what devise and where probes were touched, etc.
Name the place and the connector as well as a pic, but not just a pic.
6. Have you done anything at the connectors in no.1?

It is VERY hard to diagnose your problems if you have added, altered or removed the original wiring scheme/method per the original wiring diagram. This does not mean a person can not add accessories or an alternator. So try to explain any difference you see from my list and show pics of the differences or anything you see I haven't mentioned. Remember your DETAILED answers and pics are all I have to work with.

Your truck has four headlights as you know. The outside two are Hi/Lo Dual filament. The insides are Single filament Hi. Sealed beam.
You show 90W/100W halogen bulbs. All four would be dual wattage. Depending on how wired, could be 400W! (33A) or 380W (31A) That is unnecessary and overkill to the max. Two issues emerge:
1. Headlight switch is probably rated at 30A and needs to also handle tail lights. Hence the Relay.
2. Amperage generation has to keep up with those high amp draw lights as well as heater, radio, etc. This may require a high output alternator. Relay has no effect on that issue.

A "normal" halogen, LED or sealed beam have about the same amp draw. 4 lights Approx. 20W
All above are at Hi beam. Some LED's are way low in amp draw.

Your Halogen lights will blind on-coming drivers, their passengers and pedestrians.