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72 Mach 1 - 351C - What goes through this hole in the firewall?

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Any clues what goes through this hole in the firewall? I noticed it when I removed the shocker tower supports while replacing the front shock absorbers in my 72 Mach 1.

My car is a California build so has all "California Emission System" installed, so heaps of extra wiring etc. I also have a stray brown wire on the engine that I suspect should go through this hole.

The top arrow shows where the shocker tower support bracket bolts to the firewall. So the hole / what ever goes through it cant easily be seen.

The left arrow is the hole I'm talking about.

Any advice would be appreciated. 


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A quick look at my 73 Coupe shows a rubber plug with a brownish wire coming out and connecting to the harness on the driver side of the engine behind the carb accelerator cable bracket. 

"Yes dear", has kept me in the hobby a long time...

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Does the car have air cond ? Or DID it have a/c ?  I'm picking the brown wire would be connected to the compressor drive and activates the magnetic clutch when the a / c is turned on.   Yes, there was a rubber grommet to secure it through the firewall.  If it is ( was ) the wire to the a /c compressor, the other end will have a black plastic female plug and be beside the left side rocker cover, near the PCV / oil filler cap.

More mysteries.


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Thanks guys.

No the car has not and does not have AC..

Looking at the pictures from David, the hole is in a slightly different location.

There is a brown wire on in the loom on the engine that looks like it has been pulled from somewhere. I suspect thats the one, I will need to pull the glove box shell out and see what I can see.

I probably need a H code California emissions, no AC car to be able to figure it out.

Thanks for the info thus far though. Most appreciated. 


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