It's about time to hookup the AC in my RX7 since the weather in N. Texas is starting to get warm and it's getting close to being daily driveable. I've got a few questions and hopefully some of you guys can provide some answers.

Most RX7 guys just hook up the stock Mazda AC pressure sensor and have a dumb AC system so the PCM has no control of the AC. I'd like to wire it so that the PCM controls the AC so it'll kickup the idle and turn the fans on when the AC cycles on and also turn the compressor off at WOT. I have my compressor, condensor, and evaporator mounted and pretty much know how I'm going to run my lines.

Mechanical hookup:

The questions I have are should the GM pressure sensor and sight glass be on the high pressure or low pressure side? I'd assume the high-side, but want to make sure before I start making lines.

The Mazda used a dryer in it's AC system and I believe f-bodies used accumulators. I have no idea what either of these do, so could someone enlighten me as to what they do and if it should be mounted on the high or low-pressure side and before or after the condensor?

Electrical hookup:

I'm running a 99 f-body harness that was modified by yours truely. Looking through the PCM pinouts it looks like there are only a handful of wires that deal with the AC.

Red PCM connector;
Pin14 - RED/BLK - A/C Refrig. Press. Sensor Signal
Pin17 - DK GRN/WHT - A/C Request Signal
Pin18 - DK GRN - A/C Status Signal
Pin43 - DK GRN/WHT - A/C Clutch Relay Control

Blue PCM connector;
Pin45 - GRY - A/C Refrig. Press. Sensor 5V Ref.

I already have the harness in the car, so I can't easily verify but it looks like the wires are hooked up as follows.

AC Pressure Sensor - 3 wires
Pin14 - RED/BLK - A/C Refrig. Press. Sensor Signal
Pin45 - GRY - A/C Refrig. Press. Sensor 5V Ref.
?????????? - Purple (no idea where this wire goes)

Compressor Connector - 2 wires
Red-Pin18 - DK GRN - A/C Status Signal
????????? - BLACK (no idea where this wire goes, ground possibly?)

Loose wires coming out of the PCM - 2 wires
Red-Pin17 - DK GRN/WHT - A/C Request Signal
Pin43 - DK GRN/WHT - A/C Clutch Relay Control

I'd assume that the two loose wires are the only things that'll need to be hooked up with one getting a signal from the AC button on the dash and one going to a relay to kick the compressor on. Could anyone do me a favor and help connect the dots please?

 

does the compressor take 5V input or 12V?

 

twelve volts to the clutch.

 

I beleive that that is the ground for compressor.. and that the other is as you found. the activation from the system/switch/pcm. I am about to setup my compressor.. using all of the OEM for my chevelle and just use the LS1 compressor.. the plan is to just use the wire from the switch to one wire and the other to the ground, cause the switch on the clutch is just + and - 12v to activate.

 

On the 2 wire compressor connector...the green one is 12v+ for clutch activation....the black wire is ground. It loops through your wiring to one of the grounds on the back of the heads (I believe driver side). The A/C request wire comes from in the cabin of the vehicle...it takes a ground request to tell the PCM to turn on the A/C. The A/C clutch relay control is a ground signal to the relay to kick the relay on, just run ign 12v+ to the other side of the relay. You should have somewhere a wire to hook up to the latching side of the relay to power the A/C clutch. I believe it takes 20 or 30 amp circuit for this. As far as the purple wire in the 3wire pressure sensor...I dont know that either, never been able to figure it out and havent searched around to find it.

 

Purple goes to the PCM RED connector pin 57 "Low Reference, AC sensor, intake Air temp". I think it is the Low reference voltage (ground) for the pressure sensor.

Grey wire PCM BLU connector pin 45 "5-volt Reference A/C Refrigerant Pressure Sensor"

RED/BLK goes to PCM RED connector pin 14 "A/C Refrigerant Pressure Sensor Signal"

Basically the 3 wires going to the pressure sensor go between the PCM and the sensor. You should not have to do anything else with them.

 

I think there are 3 wires you need to hook up.

DK GRN/WHT (PCM RED 17) A/C Request Signal AC Switch
GRN (PCM RED 18) "A/C Compressor Clutch Supply Voltage" A/C Relay (relay switched power)
GRN/WHT (PCM RED 43) "A/C Clutch Relay" A/C Relay - side

 

Thanks a lot Thaniel. My pinouts only listed Blue 57 as IAT Sensor Ground. I had an idea of what needed to be done, but didn't want to start running power to anything before I knew exactly what each wire does.

 

Thanks a lot Thaniel. My pinouts only listed Blue 57 as IAT Sensor Ground. I had an idea of what needed to be done, but didn't want to start running power to anything before I knew exactly what each wire does.