Just trying to think ahead - I’d like to add some extra wiring to my original ‘72 wiring harness before I re-install it into the car. I always struggle with electrical stuff but usually manage eventually.. but I was hoping for some recommendations to try and eliminate any “ooops!” moments later.
Im gonna have to figure out stuff like preferred gauge of wire, inline fuse/relays, is a ground wire needed thru the harness for particular items, etc.

1. A/F Lambda sensor: both a + & - wire needed thru the harness?..where should it ground?..what gauge wire?

2. 3rd brake light: same questions ^ , also can I just tap into the already present stock wire for rear brakes?

3. Oil pressure numerical (for combo gauge), I’ll be using a dual pole sender at the engine: same questions^ and where does it ground?

4. CHT: so I think I’ll only be adding the specialized braided wire to the harness - is that right? Does a ground wire come in to play somewhere?

5. Fog lights: I need to look closer at my original harness (‘72) but I don’t think the car came with fogs originally. So same questions as above ^ .

6. Positive Battery Cable: so, rather than have a bunch of wires attached outside the + battery terminal , I’d like to get them imbedded inside the harness and shrink wrapped into the + cable’s outer shell. I believe the radio is usually one that you see here (what gauge?)… and what are some of the other stuff we usually see attached to the + side

Any help appreciated!


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Fog light wiring is built into harness. You need switch, black relay for fuse board.

Ideal harness to use would be 73 because it has the console wiring .

Thanks Mark I do have a switch already.
So I understand, can we confirm that EVERY '72 harness is gonna necessarily have fog light wiring included (if not used), and that EVERY '73 harness will have built in accommodations for a center console? I thought the harnesses were more varied than that.

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The brake light signal is present at the rear light bucket in the trunk. Use a piggyback quick disconnect spade to connect an extra wire for the 3rd brake light and route it back into the engine compartment. You can pick up ground for 3rd brake light behind the relay board.

Ahh ok, that makes since. I was imagining cutting into wire for some sort of splice. Glad I asked because this solution would have never dawned on me - thanks!


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Have to look but I may have 1 or 2 complete/incomplete 73 full harnesses.

Yeah let me know, thanks

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