Author Topic: 78 trans am wiring issues  (Read 415 times)

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Offline Anthony82

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78 trans am wiring issues
« on: May 17, 2019, 08:46:50 AM »
I'm trying to switch the aftermarket autometer fuel and volt meter back to the original. Previous owner has a rats nest of wires under the dash. He has added many wires to the original wiring harness adding more grounds and more light wiring. So theres many wires i don't need any more. Along with wires for rear defrost which i dont have and no power windows. So my question is what wires do I need for both the fuel gauge and the volt meter? Do they need grounds on the instrument as well? Also will any gray wire(light wire) work for illuminating the fuel volt gauge? I'm in desperate help please! Any pics or advice would be much appreciated. I have been trying to track down a wiring diagram( for a novice) but no avail. So pics would be great along with any advice! Thanks again

Offline b_hill_86

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Re: 78 trans am wiring issues
« Reply #1 on: May 18, 2019, 12:25:23 AM »
Yes grey wire is illumination. Assuming 77 and 78 are the same you should need a pink wire which is ignition power and tan which is the sending wire to the fuel gauge. Voltmeter appears to need ground and orange.
-Brian-

1977 Trans Am 400 4 speed hardtop

Offline b_hill_86

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Re: 78 trans am wiring issues
« Reply #2 on: May 18, 2019, 12:28:23 AM »
There used to be a service manual available through this site but honestly itís pretty dead around here now and the ďstoreĒ to purchase the manual is closed. That being said Iíd be happy to share my 77 diagram with you but Iím not sure whatís different. I also donít use photo hosting sites so Iíd have to email it to you. PM me with your email and Iíll send it over.
-Brian-

1977 Trans Am 400 4 speed hardtop

Offline Aus78Formula

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Re: 78 trans am wiring issues
« Reply #3 on: May 18, 2019, 09:26:59 AM »
Hundreds of new and used factory manuals available, cd, usb or paper. Every owner should at least have their own year model to save the rest having to upload basic details every time they want an answer.