RAM 2500 Truck 2WD V8-5.7L VIN D (2004)
Evaporator Temperature Sensor / Switch: Description and Operation
The evaporator temperature sensor is a two-wire temperature sensing element located at the coldest point on the face of the evaporator. The sensor is
attached to the evaporator coil fins. The evaporator temperature sensor prevents condensation on the evaporator coil from freezing and obstructing A/C
system air flow. The evaporator temperature sensor cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.
The evaporator temperature sensor monitors the temperature of the evaporator. The sensor will change its internal resistance in response to the
temperatures it monitors. The A/C-heater control module is connected to the sensor through a sensor ground circuit and a sensor signal circuit. As the
evaporator temperature increases, the resistance of the sensor decreases and the voltage monitored by the module decreases. The module uses this
monitored voltage reading to an indication of the evaporator temperature. The A/C-heater control module is programmed to respond to this input by
cycling the air conditioning compressor clutch as necessary to optimize air conditioning system performance and to protect the system from evaporator
freezing. The external location of the sensor allows the sensor to be removed or installed without disturbing the refrigerant in the system. The evaporator
temperature sensor is diagnosed using a DRBIII(R) scan tool. Refer to Body Diagnostic Procedures.
