Hi everyone. I am a new FD owner as of December. I’ve been trying to figure out why the AC doesn’t work. Something seemingly off(?) I noticed is that on the AC relay I am getting 12v to NO and COIL, nothing on COM. I thought COM should have power? Relay clicks when AC turns on. I’ve been able to confirm the compressor itself is ok and my PFC is passing the ac sensor check on all fan speeds. Does this mean the pressure check has passed? I tried jumping NO to COM and I’m still getting 0v on the compressor before and after the pressure switch (blue connector). Any advice here? I’ve tried to piece together info from other threads but the relay pin power is confusing me. Thank you!

 

Page Z-68 of the 1994 wiring diagram shows the AC clutch relay. There are two fuses that send power into the relay: The 15A Air Cond fuse in the engine bay sends 12V power into the Yellow wire (power in to the relay), and 15A Cigar fuse inside the cabin sends 12V into the Blue/Black wire (coil 12V side). The coil trigger (Yellow/Black wire) goes straight to the ECU, pin 1L. And the Black/Red wire should send 12V out to enable the AC clutch when the Yellow/Black wire is pulled to ground by the ECU.

It looks like the pressure switch goes to the AC request input, ECU pin 1E. I'm not familiar with the PFC, but I've heard that this circuit can be tricky with standalone ECUs since the input voltage may be something between 0 Volts - 3 Volts depending on the blower fan ****. I would check if the PowerFC's AC requst input is seeing the difference between the AC switch on or off, and if it never detects the switch being on I would take a look at the rest of that circuit.