Grand Prix V6-191 3.1L VIN M SFI (1998)
Ambient Temperature Sensor / Switch HVAC: Description and Operation
Automatic control of in-vehicle temperatures depends on the functioning of an in-vehicle sensor and an outside air sensor. Both sensors are temperature
sensitive thermisters whose resistance varies inversely to the temperature. The resistance value determines the signal level which is sent to the heater A/C
control. In turn, the heater A/C control microprocessor utilizes this information to develop command signals for the vacuum solenoid module,
temperature motor actuator and blower motor pulse width module.
A hose duct connects the in-vehicle sensor housing to an aspirator, and air flow from the HVAC module creates a slight vacuum at the aspirator end of
the hose. This vacuum draws in-vehicle air over the in vehicle sensor and improves the accuracy of the sensor's ability to predict cabin temperature.
