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Control System Components & Functions: Sensors

Three sensors (temperature-sensitive thermistors) are used to maintain a desired in-car temperature by means of sensor-developed electrical signals to an amplifier. The amplifier output is used to control a transducer which modulates the engine vacuum and positions the power servo diaphragm and the air mix door. The three sensors are positioned and function as follows: The in-car sensor senses car interior temperature and sun load and is positioned, along with an in-car system turn-on switch, in a grille-enclosed chimney in the instrument panel upper cover. The discharge (duct) air sensor is mounted on the mode selector case and senses the temperature of the air being discharged into the car interior by the system. The ambient sensor and compressor switch assembly is located in the air inlet assembly behind the right hand side kick-pad and senses the temperature of air entering the system.

Fig 1: Resistance Graph Of Sensors
G09310828Courtesy of GENERAL MOTORS COMPANY