Dakota 2WD V8-4.7L VIN J (2005)
Evaporator Temperature Sensor / Switch: Description and Operation
The evaporator temperature sensor (1) is an electrical thermistor located within a molded plastic case that is inserted into the HVAC housing (2) to
measure the temperature of the conditioned air downstream of the A/C evaporator (3). Two terminals within the connector receptacle connect the sensor
to the vehicle electrical system through a wire lead and connector of the HVAC wire harness.
NOTE: Cutaway of typical HVAC housing shown for clarity in illustration.
The external location of the evaporator temperature sensor allows the sensor to be removed or installed without disturbing the refrigerant in the A/C
system.
The evaporator temperature sensor monitors the surface temperature of A/C evaporator and supplies an input signal to the A/C-heater control. The
A/C-heater control uses the evaporator temperature sensor input signal to optimize A/C system performance and to protect the A/C system from
evaporator freezing. The evaporator temperature sensor will change its internal resistance in response to the temperatures it monitors and is connected to
the A/C-heater control through sensor ground circuit and a 5-volt reference signal circuit. As the temperature of the A/C evaporator decreases, the
internal resistance of the evaporator temperature sensor decreases.
The A/C-heater control uses the resistance reading as an indication that conditions are correct to broadcast an A/C request message on the controller area
network (CAN) B bus, where it is read by the front control module (FCM).
The FCM then requests the powertrain control module (PCM) to cycle the A/C compressor clutch as necessary over the CAN C bus.
The evaporator temperature sensor is diagnosed using a scan tool.
The evaporator temperature sensor cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.
