SRX AWD V8-4.6L VIN A (2004)
Evaporator Temperature Sensor / Switch: Description and Operation
EVAPORATOR TEMPERATURE SENSOR
The HVAC control module monitors the temperature of the air passing through the evaporator by the A/C evaporator air temperature sensor. This sensor
is located on the evaporator core. The temperature is used to cycle the A/C compressor ON and OFF to prevent the evaporator core from freezing. A
thermistor inside the sensor varies its resistance to monitor the evaporator air temperature. The HVAC control module monitors the voltage drop across
the thermistor when supplied with a 5-volt reference signal. The HVAC control module will send a class 2 message to the ECM to stop requesting the
A/C compressor clutch operation if the temperature drops below 3°C (37°F). The sensor must be above 4°C (39°F) to request the A/C compressor
clutch again.
The sensor operates within a temperature range between -40°C to 215°C (-40 to 355°F). If the HVAC control module detects an open in the evaporator
temperature sensor or circuit, the class 2 message sent to the ECM will not submit the A/C ON request. The HVAC control module will then send a
request to the Radio for display of the SERVICE A/C SYSTEM that will be displayed on the DIC. The HVAC control module will also display A/C
OFF on the module as long as the condition is present.
