Ambient Temperature Sensor / Switch HVAC: Description and Operation

OUTSIDE TEMPERATURE SENSOR

Basic 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 thermistors whose resistance varies inversely to the temperature. The resistance value determines the signal level which is sent to the Air Conditioning (A/C) control assembly.

Command Signals
In turn, the A/C control assembly microprocessor utilizes this information to develop command signals for the vacuum solenoid module, temperature motor actuator and blower motor power module.

Aspirator
A hose duct connects the in-vehicle sensor housing to an aspirator, and air flow from the Heater, Ventilation, and Air Conditioning (HVAC) module creates a slight vacuum at the aspirator end of the hose. This vacuum draws in-vehicle air over the sensor and improves the accuracy of the sensor operation.