[jahblah90]

Bought a 77’ Formula, and these wires were cut as seen. Are they necessary for anything to get the car running? I’m thinking MAYBE they go to the AC box or something, but couldn’t find anything online to verify.

 

[1993TransAm]

What colors are they?

 

[b_hill_86]

I’m thinking you’re right about AC. I’m not home to check my 77 but I can try to remember to look after work tonight.

 

[Aus78Formula]

Yes, AC harness. It's separate to the main harness so not a major drama to replace. Annoyingly, there's a plug just on the other side of the grommet but looks like they wanted to keep firewall sealed. There were a few variations and changes during 77 and early 78 with changing of switch locations and air sensors, but can be made to work. Just need to confirm with other harness layout/plugs if it was early or late harness. Don't go off shop listings without confirming elsewhere. I noticed even when looking this up that they have another ad of similar but wrong pic.

Do you have a 77 wiring diagram/Service Manual?

It would have been similar to this. In 77 they introduced different engines and layout so kept adjusting things to suit instead of one single harness.

1977 - 1978 Firebird Air Conditioning Harness, Engine Side

New air conditioning wiring harness for your 77 - 78 Firebird or Trans Am. This is the engine compartment section. You may also need the compressor jumper wire harness shown below to complete the circuit.

www.firebirdcentral.com

https://www.classicindustries.com/product/all-years/pontiac/firebird/parts/fb72728.html

This would be on the dash side connected to it, runs to heater controls and main harness. 78+ is very similar but a wire or two in different locations so best to check plugs and arrangement to know which version you have. I think it was a late-77 change rather than day of new model.

FB76165 - 1977 AC Extension Harness

This is a correct reproductions of the original air conditioning wiring harnesses which were used on factory optional air conditioning. Each harness will duplicate the original in every detail including correct color wiring. Note: For use with factory original air conditioning systems only...

www.classicindustries.com

 

[jahblah90]

awesome, thanks everyone for the replies. I won’t be using AC in the car. I bought it with the wires cut, so I just wanted to make sure they weren’t essential to running the vehicle. Just dropped my engine in today finally so it’s good to know that I don’t need those wires

 

[Aus78Formula]

But as a result you probably have no fan either, it normally grounds to the compressor brackets on AC vehicles. Find out which one this wire is and run it to ground, should see it kick up.