Continuing on, if it's electrical:
1. The control head sends 12v. to the Green/Orange wire at the cycling switch when A/C is on. Is it there? If not, the problem is in the head or wiring from it.
2. This 12v. leaves the closed switch via the Purple wire and goes to the "Integrated Relay Control Module" (that's the black box on top of your rad. It controls A/C and cooling fan, among other things). Still got 12v there? If not, trace the wire for an open.
3. Check for powers to the IRCM. 2 Black/Orange, a Brown, and a Yellow will be hot at all times. A Red/Green will be hot in run. If not, check fuses L,G, or F in the underhood fuse box or open wiring. Everything good there?
4. Check output from the IRCM. Disconnect the clutch and check for 12v. across the 2 wires at the clutch connector. If no, and the wires between there and the IRCM are OK, replace IRCM. If yes, the clutch field is NFG.
One other thing- the PCM cuts the compressor out at 90% throttle. Are you having any TPS problems (false WOT)? Is your Check Engine light on?
Hope this helps!