Evaporator Temperature Sensor: Operation

WARNING: This page is about a different car, the 2005 Dodge Stratus and 2005 Chrysler Sebring. However, it is still accessible from the selected car via links, so may be relevant.

The evaporator temperature sensor is a thermistor that operates on a 5-volt reference signal sent out by the body control module (BCM). The evaporator temperature sensor connects to the BCM through a two-wire lead and connector of the HVAC wire harness. The evaporator temperature sensor monitors the temperature of the A/C evaporator and changes its internal resistance in response to changes in the evaporator temperature. In turn, the change in the sensors internal resistance changes the reference signal voltage read by the BCM.

The BCM uses the reference signal voltage as an indication that conditions are correct to request A/C operation, should the operator (manually) or the A/C-heater control (automatically) so desire this function. In turn, the BCM broadcasts the A/C request on the programmable communications interface (PCI) bus, where it is read and processed by the powertrain control module (PCM). The PCM will check engine coolant temperature and refrigerant pressure temperature before activating the A/C compressor clutch.

The evaporator temperature sensor is diagnosed using a DRBIII® scan tool. Refer to the BODY DIAGNOSTIC PROCEDURES - EXCEPT COUPE article.

The evaporator temperature sensor cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.