a/c problem with my 92 Nissan 240sx Works on direct power, but not working?

[mazersx]

I am currently having the same problem on my 92 240. The AC light comes on, the engine goes into a fast idle, but the air temperature remains the same. There is coolant in the system (I'm unsure if the PSI is correct, I had a friend check it), the relays have been replaced, all fuses are fine, however the AC clutch still doesn't engage. Using a lead wire I can manually engage the clutch. The low pressure switch on the canister (next to the sight glass) is ok. Any ideas?

[Sileighty_85]

check the thermo control amp. Located on the "Cooling Unit" Evaporator box under the dash. its a small rectangle box

[iLagX]

That should be it!
Most of the time it is thermal control amplifier.

[mazersx]

check the thermo control amp. Located on the "cooling unit" evaporator box under the dash. Its a small rectangle box

got it thanks man!!