I have 2000 Malibu base model. ac compressor won't engage. 134a pressures are good. I now am suspect that the heater/ac control assy. may be my problem. according to the schematic there is a LT GREEN wire connected to the control assy. that is marked as A/C REQUEST. Does anyone know if this wire should be (+pos.) or (-neg) when ac is turned on and what should the voltage be? The strange thing is that when I turn the ac on, the green ac indicator light on the control assy. comes on, but no compressor. (Again system is fully charged) I have checked the LT green wire with 12v test light and get nothing when turning ac on and off. Thinking about placing a jumper wire (with correct voltage with either + or -) to LT GREEN wire to see if compressor engages, but want to be sure before I do so. I have had to take out control assy 3 times over the years to clean brass rotary contacts. I am experienced with electrical relays/switches/contactors ect, but am totally lost when it comes to an electronic printed curcuit. I hope someone here can help me.

See if you have 12v going into your LOW/HIGH side pressure switches. If you have voltage, its supposed to go through the CLOSED LOW side switch and through the CLOSED HIGH side switch. Low side switch will open around 10 psi or so. High side is designed to open beyond 500 I think. Check for continuity on both switches. They should both be closed.

No low side pressure switch on this model. only high side pressure switch with 5v reference. it is good.

fixed: faulty pressure transducer was problem

Thanks for letting us know what the fix was, appreciated!