A/C mode switch voltage problem

["Jonathan Lazar" <jxace@xxxx>]

I have run into a very weird problem while trying to figure out why my A/C
compressor doesn't engage.

Here is some background info first; I have owned the car for 2 years and the
A/C has never worked, however, the vent system did. I was able to blow
fresh air through the vents on all four of the blower speeds. I know the
compressor works because I can supply a 12 volt source to the wire coming
off the compressor and it will engage until I remove the 12 volt source.

The A/C mode switch supplies 12 volts to the compressor circuit and the
blower circuit when the mode switch is on the MAX setting. But, the moment
the fan speed switch is turned to any speed, the circuit grounds and I lose
all volts from the A/C mode switch. Because of this, the compressor doesn't
get any volts and the blower motor doesn't get any volts. All wiring, the
mode switch, fan speed switch, the blower motor, and the 3rd and 4th relays
check out perfectly.

I am at a loss. Why are the volts at the mode switch lost when the fan
speed switch is turned to any one of the speeds?

Any help is appreciated.

Jonathan Lazar
VIN# 4494