# 1970 GTO Wire Harness



## 1GTO2NV (Apr 20, 2014)

So that time has come I can no longer avoid it - the old girl needs a wiring update.. Last summer was a bummer due to slow voltage drain/shorts weird "Christine" like lighting behavior. My issue started with some headlight shorts which I managed to rewire and make work. Now left with a pesty passenger running light short that will not go away despite me tracing and rewire some of the front harnesses. So I have decided time to stop patching and rip it out and install new wire-harness - Just not sure if I should just do the headlight kit or an entire harness kit.. My dash is behaving badly as well very dim now. My alternator while running the car hovers at 12.2 V not sure that is normal but according to Google search, it is not. Looking for tips wire harness recommendations - Ames / American Autowire / Painless ?? I have all the tools and the patients of Jobe so I think i can do it... I will burn a lot of Buron no question..


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## pontrc (Mar 18, 2020)

Went with Ames and OPGI both sold the harness that M&H made Which is a good product. Correct color coding and plugs


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## armyadarkness (Dec 7, 2020)

The only thing that concerns me, is that you havn't really located your problem. So... if you have a bad ground, headlight switch, or conncetion somewhere, you could replace the headlight and engine bay harness, and still not solve your issue. As for what you should get, that also depends on what you're doing. If you've converted to HEI (or would like to), now is the time to get an HEI harness... Adding the required HEI wires later, sucks.

Also, are you happy with your stock T3 headlights? If you're looking to upgrade them to modern visibility lighting, then you can easily make your own headlight harness. Heck, even if you're not upgrading the beams, you can still cheaply make your own harness.

The parts themselves are easily available at the resto sites and Amazon, but think it through, first. 

A good alternator puts out at least 14 volts, but where you check it matters. I've not seen an OEM headlight switch, pass the full 14 through it, so if you're checking downstream of that, then you're not getting an accurate reading.

I would pull your bulkhead connectors apart and see what it looks like. A simple blast of contact cleaner and some dielectric grease, could be all you need to run like new. 

If you're looking to update the lights, I can send you the schematic for the harness that I made. It's cheap, easy, and very effective at tremendously increasing your light.


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## O52 (Jan 27, 2019)

I bought from M&H for my engine harness and extra wiring to build my own headlight harness. American Autowire had the correct terminals for the headlight sockets.

I plan to use the Repo T3 headlights (still have my originals btw). Supposedly they are brighter than the original design. 
When rewiring the headlight harness, I didn't want the relays under the hood. I used 12 gauge wire from under dash mounted 30 amp relays to the firewall plug to the headlights. Relays are triggered by the dimmer switch and powered from a fuse panel mounted circuit breaker normally used for power accessories. 

The original dash and rear lighting harnesses were in excellent condition. I verified continuity, replaced terminals as needed and rewrapped the harness with new tape.


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## Noangelbuddy (Dec 6, 2017)

I went with American Autowire for my 65 GTO. Good quality product and instructions. Had a problem with a miswired ignition plug (it was simple to correct). Their technical support team was quick to respond to questions, which can be a lifesaver if wiring is not your strong suit.


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## pontrc (Mar 18, 2020)

I agree with army on the issues he mentioned especially the hei which they make the harness for HEI and standard. But if this harness is original and 50 + years old probably good idea to replace it. Engine compartment especially wires insulation break down over time.


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## JamesGTO66 (Jun 16, 2020)

1GTO2NV said:


> So that time has come I can no longer avoid it - the old girl needs a wiring update.. Last summer was a bummer due to slow voltage drain/shorts weird "Christine" like lighting behavior. My issue started with some headlight shorts which I managed to rewire and make work. Now left with a pesty passenger running light short that will not go away despite me tracing and rewire some of the front harnesses. So I have decided time to stop patching and rip it out and install new wire-harness - Just not sure if I should just do the headlight kit or an entire harness kit.. My dash is behaving badly as well very dim now. My alternator while running the car hovers at 12.2 V not sure that is normal but according to Google search, it is not. Looking for tips wire harness recommendations - Ames / American Autowire / Painless ?? I have all the tools and the patients of Jobe so I think i can do it... I will burn a lot of Buron no question..
> View attachment 140334


Dude she is absolutely gorgeous 😍😍


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## 1GTO2NV (Apr 20, 2014)

JamesGTO66 said:


> Dude she is absolutely gorgeous 😍😍


Thank you brother...


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## 1GTO2NV (Apr 20, 2014)

armyadarkness said:


> The only thing that concerns me, is that you havn't really located your problem. So... if you have a bad ground, headlight switch, or conncetion somewhere, you could replace the headlight and engine bay harness, and still not solve your issue. As for what you should get, that also depends on what you're doing. If you've converted to HEI (or would like to), now is the time to get an HEI harness... Adding the required HEI wires later, sucks.
> 
> Also, are you happy with your stock T3 headlights? If you're looking to upgrade them to modern visibility lighting, then you can easily make your own headlight harness. Heck, even if you're not upgrading the beams, you can still cheaply make your own harness.
> 
> ...


You are 100 % right.. I did upgrade the HEI as well as the headlights... I have redone most of the wiring since I wrote this and invested in some tracing tools.. which will be the job next week... So I have a slow drain... plus my Alternator cant hold anything above 12.5... I was thinking of installing a Delco Alternator Anti-Feed Back Diode Harness Plug 10SI 12SI 15SI 27SI Regulator... any thoughts







?


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