Hi guys just purchased a 1998 GMC JIMMY 115000kms on the clock, and
everytime I switch on the windshield defroster there is no heat coming
through because the A/c compressor turns on. Then when I turn the knob to
dash vents compressor shuts down and normal heat blows out. The A/C works
great when in it's position. So can anyone help me figure out why the A/C
compressor turns on when I turn the knob to defrost ?
It's supposed to do that. The incoming air hits the A/C evaporator first,
which removes the moisture from the air, then it hits the heater core which
heats it before blowing out your vents. The A/C compressor helps dry the
air so your window defogs faster and stays fog-free even in very humid
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