A/C Compressor

WARNING: This page is about a different car, the 2009 Dodge Caliber. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: 5SE12C Compressor

Courtesy of CHRYSLER LLC

NOTE: Typical clutchless Denso A/C compressor shown.

The 5SE12 and 6SEU16 A/C compressor are Variable Displacement Compressors (VDC). These compressors are driven by the engine through a drive hub (1) and pulley (2) and do not require the use of an electromagnetic clutch, as they use an integral control solenoid (3) to automatically adjust the angle of the swash plate (5) to reduce or increase the stroke of the pistons (4).

The A/C compressor draws in low-pressure refrigerant vapor from the A/C evaporator through its suction port. It then compresses the refrigerant into a high-pressure, high-temperature refrigerant vapor, which is then pumped to the A/C condenser through the compressor discharge port. The A/C compressor is lubricated by refrigerant oil that is circulated throughout the refrigerant system with the refrigerant. See Heating and Air Conditioning/Plumbing/OIL, Refrigerant - Description .

The A/C compressor is controlled by the Powertrain Control Module (PCM) or Engine Control Module (ECM), depending on engine application. The PCM/ECM calculates compressor displacement required by A/C system load and demand by monitoring vehicle speed, A/C high side pressure, engine speed, evaporator temperature, accelerator pedal position, ambient temperature and A/C-heater request signals. The PCM/ECM then sends a Pulse Width Modulated (PWM) signal to the A/C compressor control solenoid to increase or decrease refrigerant flow through an orifice located within the compressor housing. The amount of refrigerant allowed to pass through the orifice in the compressor determines the head pressure which controls the angle of the swash plate, which in turn, determines the amount of compressor displacement. When there is no demand for A/C, the swash plate is adjusted to nearly a zero degree angle, which removes compressor torque drag from the engine.

This A/C compressor will reduce the displacement of the compressor based on ambient air temperature. For example; as the outside temperature falls from 27° C (80° F) to 19° C (66° F), the amount of refrigerant flow required through the A/C orifice valve to keep the A/C evaporator cool becomes less, and the swash plate is adjusted to a lower angle, which reduces compressor displacement. However, due to the lower outside air temperature, panel air outlet temperature will not noticeably change.

The A/C compressor control system is diagnosed using a scan tool. Refer to DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Diagnosis and Testing .

CAUTION: Do NOT run the engine with a vacuum pump in operation or with a vacuum present within the A/C system. Failure to follow this caution will result in serious A/C compressor damage.

CAUTION: Be certain to adjust the refrigerant system oil level when replacing an A/C compressor. See Heating and Air Conditioning/Plumbing/OIL, Refrigerant - Standard Procedure . Failure to properly adjust the refrigerant oil level can prevent the A/C system from operating as designed and can cause serious A/C compressor damage.

NOTE: The compressor drive hub and the pulley and bearing assembly can not be serviced separately from the A/C compressor. In the event of drive hub or pulley and bearing assembly damage or failure, the A/C compressor, drive hub and pulley and bearing must be replaced as an assembly.

The A/C compressor cannot be repaired and must be replaced if inoperative or damaged. If an internal failure of the A/C compressor has occurred, the A/C accumulator and the A/C liquid line must also be replaced. See Heating and Air Conditioning/Plumbing/ACCUMULATOR - Description and Heating and Air Conditioning/Plumbing/LINE, A/C Liquid - Description .