Control System Inputs

A/C Ambient Air Temperature Sensor
The A/C ambient air temperature sensor and bracket:
- is located in front of the A!C condenser core near the center of the vehicle.
- contains a thermistor which measures the temperature of outside air as a resistance and sends that reading to the electronic automatic temperature control assembly.

In-Car Temperature Sensor
The in-car temperature sensor, which is part of the message center control panel, operates in the following manner:
- A thermistor in the in-car temperature sensor measures air temperature inside the passenger compartment.
- An automatic temperature control sensor hose and elbow is connected between the A/C evaporator housing and the in-car temperature sensor.
- The automatic temperature control sensor hose and elbow takes air from the A/C evaporator housing air stream to create a suction in the in-car temperature sensor.
- The suction draws in-vehicle air into the in-car temperature sensor and across the thermistor.

A/C Sunload Sensor
The A/C sunload sensor:
- is located on the top RH side of the instrument panel above the glove compartment.
- contains a photovoltaic diode that is sensitive to light.
- has some unspecified resistance across the terminals depending upon the amount of light reaching the photovoltaic diode, therefore the only test that can he performed is for an internal short circuit.

A/C Cycling Switch
The A/C cycling switch is mounted on a Schrader valve-type fitting on the top of the suction accumulator/drier.
- A valve depressor, located inside the threaded end of the A/C cycling switch, presses in on the Schrader valve stem.
- This allows the suction pressure inside the suction accumulator/drier to control the operation of the A/C cycling switch.
- The electrical switch contacts open when the suction pressure drops to 152-193 kPa (22-28 psi).
- The contacts close when the suction pressure rises to 276-324 kPa (40-47 psi).
- When the A/C cycling switch contacts close, the signal to energize the A/C clutch is sent to the powertrain control module through the electronic automatic temperature control module.
- When the A/C cycling switch contacts open, the A/C clutch field coil is deenergized and compressor operation stops.
- The A/C cycling switch will control the A/C evaporator core pressure at a point where the plate/fin surface temperature will be maintained slightly above freezing.
- This prevents icing of the A/C evaporator core and blockage of airflow.
- It is not necessary to discharge the refrigerant system to remove the A/C cycling switch.

A/C Pressure Transducer
The A/C pressure transducer is mounted on a Schrader valve-type fitting on the A/C compressor to condenser discharge line.
- A valve depressor, located inside the threaded end of the A/C pressure transducer, presses in on the Schrader valve stem.
- This allows the compressor discharge pressure to be monitored by the powertrain control module.
- The A/C pressure transducer provides a voltage signal that is proportional to the A/C compressor discharge pressure.
- The powertrain control module uses this information for A/C clutch control, cooling fan control and idle speed control.
- It is not necessary to discharge the refrigerant system to remove the A/C pressure transducer.