I have a 2007 Ford Five Hundred, 3.0L DOHC Duratec V6 with the 6spd Trans. My problem is that the A.C Compressor does NOT come on. I am very mechanically inclined and here's the process I've done this far.
*I've tested the 2wire (green/black) to the A.c clutch and is has NO power to it.
*I've check ALL fuses and relays. More then once
*I've replaced the A.C pressure switch(3wire on the compressor line)
*I've replaced the Cabin Air temp sensor, located in the EVAP box.
*I've checked the A.C Freon level. Not running I can't get an accurate read but it has enough to start

I still get NO power to the A.C clutch this is won't engage. Can anyone help me plz? Thank you so much

 

I appreciate all the help and info. You are extremely knowledgeable. Thanks. I was able to find a diagram and verify that following your procedures by jumping it the A.C Compressor did engage. Which leads me to believe it's the PCM. Is this a common problem for the PCM to fail and effect the Air Conditioning system ONLY? Also do you know of a place where I could get an affordable PCM with keys? Thanks again

 

You supplied a ground for the A/C clutch relay?
The climate module supplies an A/C allowed request signal to the cluster, which relays the request to the PCM.