Compressor HVAC: Description and Operation

This A/C system uses a vane-type Panasonic A/C compressor. The A/C compressor is belt driven by the A/C clutch pulley. A magnetic clutch engages the A/C compressor shaft. When voltage is applied to the A/C clutch field coil, the clutch hub is drawn by magnetic force toward the A/C clutch pulley, which rotates freely on the A/C compressor. The magnetic force locks the clutch hub to the A/C clutch pulley to turn the A/C compressor shaft. When voltage is removed from the A/C clutch field coil, the clutch hub moves away from the A/C clutch pulley and the A/C compressor shaft ceases to rotate. Features of the A/C compressor include:
- Little friction loss.
- Compact size.
- Quiet operation.
- Few parts.

Compressor operation is controlled by the A/C evaporator core orifice and the A/C cycling switch. However, when the A/C is operating and the engine coolant reaches 113°C (236°F), the Powertrain Control Module (PCM) will cycle the A/C clutch control relay on and off for 10 second intervals. The A/C clutch control relay will then cycle the A/C clutch field coil on and off for 10 second intervals until the coolant reaches 107°C (225°F).

The A/C compressor features a sludge control valve which prevents compression of liquid in the refrigerant. If refrigerant mixed with liquid enters the rotor housing and the refrigerant pressure increases abnormally, the sludge control valve opens, allowing the liquid to escape. The liquid then flows to the suction accumulator/drier along with the refrigerant.

A thermal protection switch, fitted to the exhaust port, monitors the A/C compressor temperature and prevents the A/C compressor from overheating. If the temperature in the A/C compressor exceeds 165 +/- 4°C (329 +/- 39.2°F), the thermal protection switch opens the magnetic A/C compressor clutch circuit to stop the A/C compressor operation. If the temperature drops to less than 147 +/- 4°C (297 +/- 39.2°F), the thermal protection switch closes the circuit, and the A/C compressor again operates.

An irregular noise results when the vanes are not pressed against the inner wall of the rotor housing. This may occur when charging from the low-pressure charging port or when replacing parts without adjusting the amount of Motorcraft Refrigerant Oil YN-12b or equivalent meeting Ford specification WSH-M1C231-B.

If the A/C compressor main housing requires service, the whole A/C compressor must be replaced.

NOTE: Whenever an A/C compressor is replaced, it will be necessary to replace the suction accumulator/drier.