Air Conditioning: Notes

WARNING: This page is about a different car, the 2004 Mercury Monterey and 2004 Ford Freestar. However, it is still accessible from the selected car via links, so may be relevant.

The main A/C refrigerant system is a clutch cycling orifice tube type and the auxiliary A/C refrigerant system is a thermostatic expansion valve system. The system components are:

A/C compressor (19703).
A/C condenser core (19712).
A/C evaporator core (part of 19850 assembly).
suction accumulator (19C836).
connecting refrigerant lines.

The refrigeration system operation is controlled by the:

evaporator core orifice tube (19D990).
A/C cycling switch (19E561).
A/C pressure transducer (19D594).
thermostatic expansion valve (19849).

The refrigerant system incorporates an A/C compressor controlled by the powertrain control module (PCM) through an A/C clutch relay.

The A/C cycling switch senses evaporator core pressure to control A/C compressor operation.

An evaporator core orifice tube is installed in the condenser to evaporator line (19835) to meter the liquid refrigerant into the evaporator core.

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

The climate control assembly is set to a mode which provides an A/C request to the PCM.
The A/C cycling switch is not open due to a low than acceptable pressure on the low pressure side of the refrigerant system.
The A/C pressure transducer is reading an acceptable pressure in the high side of the refrigerant system.
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.

An A/C compressor pressure relief valve is installed in the compressor manifold and tube assembly (19D734) to protect the refrigerant system against excessively high refrigerant pressures.