A/C Temperature Sensors

The HVAC control processor monitors the refrigerant temperature and sends the data to the PCM on the class 2 serial data circuit. The PCM monitors the A/C high temperature sensor signal along with the coolant temperature sensor in order to determine the need for the cooling fans and prevents the A/C compressor from operating at high discharge pressures. A 5 volt reference signal is sent from the HVAC control processor to the A/C refrigerant high temperature sensor over the A/C refrigerant high temperature sensor signal circuit. A thermister inside the sensor varies the voltage. That varied voltage provides a signal to the software inside the HVAC control processor. Remaining voltage from the A/C refrigerant high temperature sensor is sent back to the HVAC control processor ground through the low reference circuit.

The HVAC control processor monitors the A/C low temperature sensor to determine the low side pressure based on the pressure/temperature relationship of the R-134a. A 5 volt reference signal is sent from the HVAC control processor to the A/C refrigerant low temperature sensor over the A/C refrigerant low temperature sensor signal circuit. A thermister inside the sensor varies the voltage. That varied voltage provides a signal to the software inside the HVAC control processor. Remaining voltage from the A/C refrigerant low temperature sensor is sent back to the HVAC control processor ground through the low reference circuit.