Patriot 2WD L4-2.4L (2009)
Evaporator Temperature Sensor / Switch: Description and Operation
Evaporator Temperature Sensor - Operation
OPERATION
The evaporator temperature sensor monitors the surface temperature of A/C evaporator and supplies an input signal to the Cabin Compartment Node
(CCN). The CCN 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 CCN 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 CCN uses the monitored voltage reading as an indication of evaporator temperature. The CCN is programmed to respond to this input by requesting
the Powertrain Control Module (PCM) or the Engine Control Module (ECM) (depending on engine application) to cycle the A/C clutch off and on as
necessary to optimize A/C system performance and to protect the A/C system from evaporator freezing See: Compressor HVAC/Description and
Operation/A/C Compressor - Operation.
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.
