Pacifica V6-3.8L (2008)
Evaporator Temperature Sensor / Switch: Description and Operation
Operation
OPERATION
The evaporator temperature sensor is a thermistor that operates on a 5-volt reference signal sent out by the A/C-heater control. The sensor connects to
the A/C-heater control through a two-wire lead and connector of the HVAC wire harness. The sensor monitors the temperature of the conditioned air
downstream of the A/C evaporator and changes its internal resistance in response to changes in the air temperature. As the temperature increases, the
sensor's resistance decreases which increases the reference signal voltage read by the A/C-heater control. As the temperature decreases, the sensor's
resistance increases which decreases the reference signal voltage read by the A/C-heater control.
The A/C-heater control also 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. The A/C-heater control module is programmed to respond to this input by
sending electronic messages over the programmable communications interface (PCI) data bus where it is read and processed by the body control module
(BCM), which in turn broadcasts it on the CAN C bus, where it is read and processed by the powertrain control module (PCM). The PCM then cycles
the A/C compressor clutch as necessary to optimize A/C system performance and to protect the system from evaporator freezing.
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 is diagnosed using a scan tool.
The evaporator temperature sensor cannot be adjusted or repaired and must be replaced if found inoperative or damaged.