AC compressor relay location?

[Jay340]

Do any of you guys or gals have a B with an AC relay setup? I'm restoring a 72 Charger and the owner of the car supplied all of the wiring harnesses, one of which is a compressor relay "overlay" harness. I called M+H who make the harnesses and the CS rep couldn't even find the part number in their catalog. He said that he cannot recall many of them being sold and that the relay setup could just be a very rare occurrance. The most he could give me is that the power lead goes to the starter relay stud and the ground lead mounts to the wiper motor stud. Does anyone know where the relay would mount? I assume it mounts to the firewall, but not sure where. I don't think this car had one originally, but I may install it anyway to keep the electrical stress off of the dash switches. Any help would be much appreciated.

Thanks!

 

[mopar 3 B]

Not sure why it would have an AC relay. Chargers normally would not have come with climate control. That leaves two circuits for the basic AC one for the fan the other for system pressure and compressor clutch.

 

[Jay340]

This one is an SE and has quite a few bells and whistles. The manual I have has a small sub section on how the AC system is wired. One diagram has the system wired as Dash Switch-Cutoff Switch-Compressor. The other has Dash Switch-Cutoff Switch-Relay-Compressor.

The relay itself is a factory-looking piece, so I don't think it would look totally out of place under the hood. I just don't recall ever seeing one on a car. Like I said, I would just like to keep the electrical stress off of the old switches.

 

[72RoadrunnerGTX]

There are no relays involved with the A/C system in '72, two supplemental wiring harnesses were added to the engine compartment and dash. Two wires running from the bulkhead connector, one to the low pressure switch on the dryer, then a single wire on the clutch. Another wire ran to the fan motor, with the motor ground connected to a wiper stud. Another harness was added to the dash wiring, corresponding to the bulk head connections running to the heater/AC switch and the fan resister pack. Nothing connected to the starter relay.
The FSM has fairly clear wiring diagrams for the A/C additions.

The dash A/C add-on;