# 1966 Rally Gauges wiring issue



## gtoearl (Dec 21, 2009)

Well...here we go guys.........some of you may remember some of my past posts. I mentioned that I'm going to install Vintage Air , new Gardner Exhaust and Rally Gauges with harness into my 1966 GTO. I have a question concerning the rally gauges. I have been able to score a really nice used set of rally gauges and harness. The harness has never been cut and came to me complete with the original wrapping and tape labeling... I'm really pleased with the purchase. My question is: I have a wiring diagram from classicwirring.com. It doesn't show rally gauges. I have a new engine harness. When I bought it I wanted to make sure that there wasn't a difference when having rally gauges...and I couldn't find a separate listing for that application. I was told that the engine harnesses are the same.....with or without rally gauges. Does the rally gauge harness (dovetail?) with the engine harness I have. The one thing I'm thinking about is the tach. How does the signal get to the tach if the engine harness doesn't have a specific wire for that...does it get there through the two wires that already connect to the positive side of the coil? Long winded, I know...but does anyone have an idea and if there are any other issue when converting lights to rally gauges..? thanks again guys....:cheers


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## geeteeohguy (Feb 2, 2008)

The engine harness and the dash harness are two different animals. The rally gauge cars have a different dash harness. I THINK that there is an adaptor available to fit the rally set up into a stock harness. Might try M&H wiring.


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## gtoearl (Dec 21, 2009)

I have the stock dash rally harness............Got it with the used gauges.....my question is how does the tach connect through the firewall to the coil?


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## BearGFR (Aug 25, 2008)

Just run a single wire straight from the tach to the output side of the coil primary (the small wire connection that goes to the distributor).

Bear


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## gtoearl (Dec 21, 2009)

Thanks Bear.....I know it has to end up there connected to the coil...but if the wires from harness (plug that's part of the harness) is there....doesn't it find its way to the coil for pick up? I'm very confused....I should have all the wires to make that connection given I have a new engine harness and original rally gauge harness including the fuse block....shouldn't it be just like the original way it was wired from the factory? The harness wires from the tack goes through the fuse block into the engine harness and to the coil...Right? I shouldn't have to do anything....But I can't find a wiring diagram to confirm how this rally gauge harness is wired.....:confused


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## gtoearl (Dec 21, 2009)

gtoearl said:


> Thanks Bear.....I know it has to end up there connected to the coil...but if the wires from harness (plug that's part of the harness) is there....doesn't it find its way to the coil for pick up? I'm very confused....I should have all the wires to make that connection given I have a new engine harness and original rally gauge harness including the fuse block....shouldn't it be just like the original way it was wired from the factory? The harness wires from the tack goes through the fuse block into the engine harness and to the coil...Right? I shouldn't have to do anything....But I can't find a wiring diagram to confirm how this rally gauge harness is wired.....:confused


Hey Bear, did a little more research and found a loose, separate one wire (Brown) with an in-line fuse that seems to be coming from the tach and is located in the harness just before the other dash harness wires go into the main fuse block. The books I've looked at indicate, *as you said,* a single wire (not part of the engine harness) connected to the output side of the coil (the wire coming from the distributor) running along the firewall and through a grommet into the passenger compartment and connected to that single brown wire with the in-line fuse. It would be nice to find that original wire with the factory ends...... Thanks much for your response and advice.


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## WhittP (Jun 19, 2013)

I believe American Autowire sells the wire you're looking for. It plugs right into that brown wire you are talking about.

Tachometer Harness We Make Wiring THAT Easy!


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## gtoearl (Dec 21, 2009)

thanks WhittP.........


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## David Drew (Apr 19, 2020)

gtoearl said:


> Hey Bear, did a little more research and found a loose, separate one wire (Brown) with an in-line fuse that seems to be coming from the tach and is located in the harness just before the other dash harness wires go into the main fuse block. The books I've looked at indicate, *as you said,* a single wire (not part of the engine harness) connected to the output side of the coil (the wire coming from the distributor) running along the firewall and through a grommet into the passenger compartment and connected to that single brown wire with the in-line fuse. It would be nice to find that original wire with the factory ends...... Thanks much for your response and advice.


Was the brown wire connected to positive or negative side of coil?


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## PontiacJim (Dec 29, 2012)

David Drew said:


> Was the brown wire connected to positive or negative side of coil?


Negative side of the coil.


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## gtoearl (Dec 21, 2009)

Yeah like you said negative side. LOL


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## Sixty7GTO (May 4, 2017)

geeteeohguy said:


> The engine harness and the dash harness are two different animals. The rally gauge cars have a different dash harness. I THINK that there is an adaptor available to fit the rally set up into a stock harness. Might try M&H wiring.


Does anyone have the gauge adapter harness schematic they would like to post? I have a rally gauge pod but not a schematic showing the difference between the non-rally and the rally gauges.


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