Definately check the system first for correct pressure. If it runs all the time (when its turned on) and blowing cold air, then i dont really see a problem...however, if its icing up, creating ice on the lines near the evaporator, or backside of the compressor, then there is probably a refrigerant level issue,or blowing hot air and the compressor is turning then the pressure switch may be at fault..... if its all good, the compressor will run all the time when the clutch is activated(turn on a/c or defrost in cabin).... pressure-wise, with a set of gauges the low side(suction side, usually near the evaporator) should run in the neighborhood of 30-35 ish psi.... if it falls below around 26 psi the pressure switch will deactivate the power going to the compressor's clutch, stopping the compressor....
______________
StingrayJim
NCM Lifetime Member #1936
Stingray's '76���������������������������� StingrayJr's '78���������������������������Lil Red '94
(click each one to see a bigger version)