Air Conditioning: Notes

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

The A/C system components are:

A/C compressor
A/C condenser core
A/C evaporator core
Suction accumulator
Connecting refrigerant lines
Evaporator core orifice
A/C cycling switch
A/C pressure transducer (4.0L)
Dual-function pressure switch (4.6L and 5.4L)
A/C compressor pressure relief valve

The refrigerant system incorporates an A/C compressor controlled by the PCM through an A/C clutch relay.

The A/C compressor clutch will only be engaged by the PCM if all of the following conditions are met:

The HVAC module is set to a mode which provides an A/C request to the PCM.
The A/C cycling switch is not open due to excessively low suction pressure in the low-pressure side of the refrigerant system.
The A/C pressure transducer is not reading excessively high discharge pressure in the high-pressure side of the refrigerant system (4.0L).
The dual-function pressure switch is not open due to excessively high discharge pressure in the high-pressure side of the refrigerant system (4.6L and 5.4L).
The A/C compressor relay is switched to the closed position by the PCM.
The engine coolant temperature is not excessively high.
The PCM has not detected a Wide Open Throttle (WOT) condition.

For information concerning operating specifications, refer to CLIMATE CONTROL SYSTEM - GENERAL INFORMATION AND DIAGNOSTICS .

An A/C compressor pressure relief valve is installed in the compressor manifold and tube assembly (4.0L vehicles) or the A/C compressor (4.6L or 5.4L vehicles) to protect the refrigerant system against excessively high refrigerant pressures.

Refrigerant flow into the evaporator core is metered by an evaporator core orifice tube.

For information concerning the refrigerant cycle and principles of A/C operation, refer to CLIMATE CONTROL SYSTEM - GENERAL INFORMATION AND DIAGNOSTICS .