HELP: A/C electrical problem w/ 1995 V-6 Firebird.

Hello, My firebird recently got an engine swap and after my compressor won't come on. I'm pretty good w/electrical so I checked the wiring diagrams. 1.A/c cruise fuse (under hood)-ok >2.swapped relays to be sure it
wasn't that-ok >3.tested the dk grn/wht wire from the a/c control switch inside: turn on & get ac-12vlts, off-nada-so that's ok.

if you are facing the car from the front on the same side as the battery? I was thinking that the guy that installed my engine might have messed up something, but everything else works. I changed the compressor and found that the old one works. If I ground the dk grn/wht wire from the rely the compressor kicks on. Could the PCM be the source of my problems or should I try the wiring first. I have already tested a fair amount of wires for shorts and they all seem fine so far, but I haven't been though them all. (Got to Dark) lol. How do you bypass the a/c temp sensor to check, and the a/c pressure sensor to check it also?
Here is a link for the wiring diagram:
http://www.charris.org/pont_95fb3.4ltr.jpg
Any help would be greatly appreciated! Thanks in advance Clay
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Is it possible that during the engine swap the freon was removed? I had to pull my compressor off during the engine swap on my '88. There isn't enough length in the hoses to leave the compressor attached to the hoses and get the engine out. If there is no gas in the system the compressor will not run.
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Oops. Didn't read that you had changed the compressor so you gassed it. You do know you have to disconnect the battery for 5 min and reconnect it after the ECM sees a low refrigerant level for a certain period of time, to reset it.
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That would be incorrect. The LP switch is not wired to the ECM, the ECM controls the compressor and the LP switch is simply wired to prevent compressor operation should there be a low charge condition, or the suction pressure drops lower than that what is required for safe oiling...such as on a winters day in defrost mode.

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