Cadillac Repair: 95 Eldorado AC compressor wont start, compressor clutch, ohmeter

Question
Hey Bill,
  Help! I replaced the AC compressor on my wife's 95 Eldorado (old one locked up totally)and new compressor clutch will not engage. I can force clutch to engage with 12v jumper to connector and system cools great. Relay is good, BUT is NOT receiving ground on actuator coil. 12v plus comes on with ignition, but no ground! Fuse WAS blown, but replaced and still no clutch engage. No ACP or BCM codes. Maybe Computer gone?
Please help!
Larry

Answer
Hi Larry,

      There really isn't too much left to check. Since you are able to jumper the compressor at the compressor connector then what I would do is remove the relay. There should be power comming from thr a/c fuse on 1 terminal. There should be power on a second terminal that comes through the high pressure switch behind the compressor. One wire goes to the compressor while the last one is the computor controlled ground for the relay. Try all the circuits and see if jumpering the 2 wires at the relay connector gets the compressor to engage.

     Also while the relay is out unplug the compressor connector and useing an ohmeter put it across the compressor connector. Then switch the leads. One way should show continuity...a close to 0 ohms reading while the other direction should be open. If that doesn't happen the a/c clutch diode which is taped into the harness near the connector could be open or shorted...that could be why the fuse blew.

      If you don't get power through the second wire then test the low and high pressure switches for being closed with your ohmeter. They should both be closed if the system has the correct ammount of freon in it.

      Try those things and see where it leads you. Let me know if you need anymore help. Bill