Warm air blows from the vents
Weak airflow from the vents
AC clutch does not engage
Compressor makes loud grinding, squealing, or rattling noises
Compressor cycles on and off rapidly
AC system trips the fuse or blows a relay
Visible refrigerant leaks around the compressor
Compressor pulley is seized or hard to turn
AC works intermittently
Cabin air is not as cold as usual
Compressor is overheating
Burning smell from the engine bay
Oil or refrigerant residue on the compressor
Check engine light or AC warning light is on
Pressure readings are abnormal during AC testing