I just completed the plumbing on the AC for a '92 Miata with Ford 5.0 engine. I didn't do the wiring on the car so I'm not sure exactly what I have. When I turn on the key, push in the AC button and turn on the blower, my test light lights when I probe either side of the connector going to the compressor, (would've thought one side would have given me 12V and the other would be a ground). I'm using the original '92 Mazda high side line from the evaporator which has the pressure switch, (it's not connected to any wiring, don't know if it would be in the open or closed position). Also, don't know how the computer interacts, (to increase idle when compressor is activated), or if it's even connected. Would like to look at a simple wiring layout from one of you knowledgeable folks who already figured this one out. Thanks

 

Mine's a 95, and I used the Ford CCRM for the A/C controls, with the stock Miata dash button to turn the a/c on just like a stock Miata. In comparing the Ford vs Miata wiring diagrams, the dash button on one completed the ground circuit and on the other one it completed the 12v power circuit. So, had to reverse the polarity of the Miata dash button so it would work with the Ford compressor. Easy to do with a simple relay.
TM