A control system for an automobile air conditioner including an air blend door for adjusting the output of the air conditioner, a vacuum actuator including a hermetic chamber and a control member, the control member being connected to control the air blend door proportionally to the pressure within the chamber, a vacuum modulator including a first valve for exhausting air from the chamber to a vacuum reservoir, a second valve for emitting air from atmosphere to the chamber and a restriction member arranged at the entrance side of the chamber, a control circuit for providing a first electrical driving signal for operating the first valve so as to open and a second electrical driving signal for operating the second valve so as to open proportionally to the difference between a selected temperature within the automobile and the actual temperature within the automobile, an integrating circuit for providing integrated outputs of the first electrical driving signal and the second electrical driving signal with a time constant determining the volume of the chamber and the diameter of the restriction and a feedback loop for applying the integrated outputs to the input of the control circuit.
To provide a vehicular air conditioning system for activating an electric heater with the output coming from an inverter by actuating a relay at a reasonable cost, a relay and an electric heater acting as electric heat source are connected in series between an output line of three output lines of an inverter and the negative side of a vehicular power supply. The electric heater employs a nichrome wire as its heating element and is used for warming the inside of a vehicle compartment. Moreover, the relay is turned ON/OFF after the output voltage of the inverter is set to zero. As a result, the durability of the relay can be improved, and this relay can be implemented by an existing one without newly manufacturing any dedicated relay so that the cost can be lowered.
An automatic air recirculation system is provided. The system activates an air recirculation door for recirculating the air within the vehicle passenger compartment by sensing the temperature of the engine coolant. The system also activates the air recirculation door by sensing the pressure or temperature in the compressor discharge line.
