Durango 2WD V6-3.7L (2009)
Evaporator Temperature Sensor / Switch: Description and Operation
Front Evaporator Temperature Sensor - Operation
OPERATION
The evaporator temperature sensor monitors the temperature of the conditioned air downstream of the 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.
On gasoline engine equipped models, the A/C-heater control uses the monitored voltage reading as an indication of evaporator temperature and 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.
On Hybrid Electric Vehicle (HEV) models, the A/C-heater control calculates an evaporator temperature target based on A/C load. This target
temperature is compared with the actual evaporator temperature sensor value. Based on this comparison, the A/C-heater control sends out a compressor
target RPM speed over the CAN B bus to the FCM. The FCM then ports the target message to the electric A/C compressor over the CAN C bus. If the
A/C-heater control does not receive the electric A/C compressor messages, a Diagnostic Trouble Code (DTC) will be set.
The evaporator temperature sensor is diagnosed using a scan tool See: Powertrain Management/Computers and Control Systems/Testing and
Inspection/Diagnostic Trouble Code Tests and Associated Procedures.
The evaporator temperature sensor cannot be adjusted or repaired and must be replaced if inoperative or damaged.
