Compressor HVAC: Description and Operation

Compressor Assembly
The compressor assembly is primary moving part of air conditioning system. If it fails, there is no compression of refrigerant, and no movement of refrigerant through system. It is located on left side of engine and is connected to engine crankshaft by a drive belt. It consists of compressor, manifold assembly, compressor clutch, and drive pulley.


Compressor Clutch
The compressor clutch engages compressor. It is a magnetic unit operated from air conditioning switch in passenger compartment. It is a serviceable, replaceable item.

With the ignition switch in ON, battery voltage is applied to the coil of the A/C relay and battery voltage through the ACC fuse is applied to the A/C switch. With the A/C switch ON and the blower switch in any position except OFF, a ground signal is sent through the normally closed contacts of the A/C thermostat to the Engine Control Module (ECM) A/C request input. Ground is also provided to the A/C ON indicator in the A/C switch.

Operating parameters permitting, the ECM will ground the coil of the A/C relay at ECM. The A/C relay is energized and applies battery voltage to the A/C compressor clutch through the closed contacts of the relay.