I have a 1993 gmc yukon. The a/c has been converted to R-134. Lately the compressor will work sometimes and sometimes not. I figured that it was low on freon so i bought a refill kit from Walmart. When i hooked up the pressure guage on the low side, the pressure is real high (100 psi). I am not sure now what is going on. If the pressure is too high, will the compressor not kick on? If i bybass the low pressure switch, the compressor will kick on and the pressure will start to drop, but only to about 50 PSI. I figure that this is probably the source of the problem. Does anyone know why pressure would be building up so high on the low side???

 

Hi
The reasons that I know are: the expansion valve stuck open.
Refrigerant overcharged
Air in the system
cooling fan faulty.

Symptoms: The discharge air is warm
the evaporator is sweating or frosting
Andre.