Warm air blows from the vents when the AC is on
AC clutch does not engage when the system is turned on
Compressor makes loud grinding, squealing, or rattling noises
Compressor cycles on and off rapidly
AC system trips a fuse or blows a relay repeatedly
Visible refrigerant leaks near the compressor
Compressor pulley is seized or hard to turn
AC pressure readings are abnormal
Cabin air cools only intermittently
Compressor body is excessively hot
Burning smell comes from the compressor area
AC works poorly at idle but not at higher speeds
Compressor clutch slips or does not spin with the pulley
Refrigerant lines show unusual frost or no temperature change
Compressor shaft or housing shows physical damage