Temperature regulator assembly and signal modulator therefor

A regulator assembly for an automatic temperature control system for the passenger compartment of an automotive vehicle. Regulation is by vacuum signal modulated by a sensor responsive to the difference between a selected temperature and the temperature of air in the passenger compartment of the vehicle. A vacuum actuator operated by the modulated vacuum signal is provided for operating an air-blend door for controlling the passage of blower driven heated and cooled air into the passenger compartment. The regulator includes a compact removable vacuum signal modulator subassembly of a bimetal temperature sensing element directly coupled to a vacuum signal modulator valve. Direct feedback of the position of the vacuum actuator to the bimetal sensing element is provided. The modulator is of the type employing balancing of the pressure forces of the vacuum signal against the bias of the bimetal element for positioning the modulator valve. The modulator valve is at equilibrium when the sensed passenger compartment temperature is at the selected value.