Heater and A/C Control Assembly

The electronic heater and A/C control assembly is the vehicle operator's control point for the electronic air conditioning system. The heater and A/C control includes soft-touch buttons for the various system operating modes (OFF, MAX A/C, NORM A/C, BI-LEVEL, VENT, HEATER, DEFOG, DEFROST), a blower speed control, and a temperature control lever. Vehicles equipped with a rear window defogger also have the system's ON/OFF switch located in the heater and A/C control. Each operating mode button contains an LED indicator that illuminates when selected. The rear window defogger button also contains an LED indicator.

The heater and A/C control is the electronic air conditioning systems brain; it sends commands to system components that control A/C compressor operation, air discharge location, air discharge temperature and blower operation.

HEATER AND A/C VACUUM SOLENOID

The heater and A/C vacuum solenoid operates the vacuum actuators to control air intake and discharge locations. Inside the A/C solenoid switch assembly are 4 solenoid-actuated vacuum valves that respond to the heater and A/C control electrical signals. The vacuum valves, in turn, vent or apply vacuum to the vacuum actuators. By energizing various valve combinations, the heater and A/C control can control whether air is directed to the floor outlets, panel outlets or defroster outlets. It also determines whether outside air is drawn into the system or inside air is recirculated.

HEATER AND A/C MODULE

The heater and A/C module is where all system air is heated, cooled, mixed together and directed to the various ducts and vents. The module consists of a housing with inlet openings, outlet openings, air passages and air valves. Vacuum actuators and an electric motor operate the air valves according to the A/C solenoid switch assembly signals.

BLOWER RELAY

When energized by the heater and A/C control, the blower speed relay applies voltage to both the blower switch and the blower resistors to enable the blower motor.

HIGH BLOWER RELAY

When energized by the blower switch, the high speed blower relay allows current to flow to the blower motor. All resistors are bypassed, and the blower runs at high speed.

BLOWER RESISTORS

The blower resistors make an assembly which contains 3 separate resistors. Blower speed is regulated by routing current through none, 1, 2 or all 3 resistors. The blower switch position determines how many resistors are bypassed.

BLOWER MOTOR

The blower motor is a DC motor whose speed is proportional to the input voltage. With low voltage the motor turns at a low speed; with high voltage the motor turns at high speed.

TEMPERATURE VALVE ACTUATOR

The temperature valve actuator follows commands from the temperature lever in the heater and A/C control to control outlet temperature. A reversible DC motor in the actuator operates the air mix valve, which blends cooled and heater air.

VACUUM ACTUATORS

The vacuum actuators are vacuum servos that operate valves inside the case. Three actuators are used: 2 single-diaphragm actuators and one double-diaphragm actuator. The actuators are mounted to the case and are connected to the solenoid switch by vacuum hoses.