GM Service Manual Online
For 1990-2009 cars only

The V5 A/C compressor is belt driven from the engine crankshaft through the compressor clutch pulley. The compressor pulley rotates without driving the compressor shaft until an electromagnetic clutch coil is energized. When voltage is supplied in order to energize the clutch coil, the clutch plate and hub assembly is drawn toward the pulley. Magnetic force locks the clutch plate and the pulley together as one unit in order to drive the compressor shaft.

When the compressor shaft is driven, the compressor pulls low-pressure, low-temperature vapor from the accumulator. The vapor is compressed into high-pressure, high-temperature vapor and pumped into the condenser. Refrigerant oil is carried with the refrigerant. The oil is used to lubricate the compressor. The compressor has a unique lubrication system. Compressor rotation acts as an oil separator, which removes some of the oil from the crankcase where the oil can lubricate the compressor mechanism.

When the engine is turned OFF after the A/C system has been operating, the refrigerant in the system flows from the high-pressure side of the expansion (orifice) tube to the low pressure side until the pressure is equalized. This may be detected as a faint hissing sound for 30-60 seconds. This is a normal condition.