964 A/C Question
 

1993 964. Not getting 12 volts to the a/c compressor.

The button on the climate control unit engages and the light comes on.

The A/C compressor fuse in the engine bay is good. The front condenser fan fuse is good as well

Not sure if the front a/c blower relay is good or not.

Any method for testing the relay or a compressor wiring diagram to check for wiring issues. Would a low pressure switch interrupt the circuit to the compressor if the system is too low on freon?

if system is too low on freon compressor wont engage

also check the connector, it gets corroded

The compressor clutch will engage at far less than 12V. My Sanden 507 pulls in at 8.2 V., I've been told it will engage at 5V.

System low on freon will disable the compressor circuit , once recharged the compressor clutch will engage ..
Bert

The A/C compressor has a relay in the rear fuse box lhs of the engine bay.
A. Test/check the relay.
B. If the relay is OK , if you quickly jump the relay the A/C clutch should engage and turn the compressor. If this works it could be as mentioned above the freon level has dropped below a cut off level, and you dont get a signal to the relay.
I made a small jump connector with an on/off switch w 30 amps fuse capacity.
( I think it is terminal 30 and 87 you jump, but check this. Was a while since I did it.)
I assume the condenser fan does not get a trigger signal if there isnt one to the compressor. You can jump this relay in the front fuse box as well to check .( I think it is 30c and 87 c for low fan speed, 30 and 87 for high speed)

Advice if you need a recharge: add some fluorescent UV dye to the system. The next time the system leaks you can easily find it with a black light. The dye is cheap and is less than an once.