You can bypass the low pressure switch by bridging the connectors together. If at this time the compressor engages you know your pressure is too low or you got a bad switch (rare) Theres also a switch in the thermostat housing that sends signal to ECU telling it to shut off the AC if the engine gets too hot, you can bypass that one too.

Like eddie said, the circuit is complex, start with the easiest things first so you can eliminate them before getting to the hard stuff..this thing goes into the ECU..been there done that.

99 Gen 2.5, fixing blown head gasket
89 SWB- 33's, ARB Front locker, SR rear locker/axle, SR F brakes, winch, WST Offroad Armor all Around, 2.85 Aussie T-case Gears (SOLD)
Sold: (2) 95 SR's, 86 SWB, 90LWB, 91 LWB
-Can Change a timing belt in my sleep..