My HVAC guy here at work is evacuating and refilling (134a) in my car for me. Do any of ya'll know what the high and low side pressure should be? And should the auxillary fan come on whenever the A/C is activated? Or just when the engine gets too warm?

The pressure(s) are 100% dependent on temperature & altitude..also the amount of refrigerant that you put into the system..

I would think that high pressure should be around 300-350 at 2500rpm in neutral..& low pressure less than 35 at the same time...

Aux fans should be on LOW speed at 230psi....

R134a charge should be 65-70% of the R12 capacity

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