Automatic Temperature Control System

Fig. 1 Automatic temperature control system components:

The Automatic Temperature Control (ATC) system provides automatic control of A/C compressor operation, air inlet door position, water valve operation and blower speeds in order to maintain passenger compartment temperature within the range selected by the operator.
The system control circuit consists of a feedback potentiometer, temperature control rheostat, and ambient and in-car temperature sensors, Fig. 1, which are connected in series to provide a variable resistance to system input voltage. The output voltage of this control circuit is applied to an amplifier which transforms the control signal into an operating voltage that is proportional to the control circuit voltage signal. The amplifier output voltage is converted to a modulated vacuum signal in the vacuum valve, the vacuum signal is applied to the power servo, and the power servo controls system operation.