Control Module HVAC: Description and Operation

Typical Programmer Assembly (Internal):

Programmer Assembly:

DESCRIPTION

The programmer converts electrical signals from the A/C control assembly into vacuum commands which position the mode, A/C-defrost, and air inlet (or "inside air") valves, all located in the air distributor assembly.

OPERATION

Vacuum is constantly applied to a programmer check valve which distributes the vacuum to four solenoid-controlled valves. When the A/C control assembly signals the programmer to change an air distributor valve, the associated solenoid is energized and vacuum is applied to a vacuum-motor actuator. The actuator, in turn, repositions its air distributor valve.

The programmer also utilizes a bi-directional DC motor, which operates on signals from the A/C control assembly that result from information from the in-car and outside air temperature sensors and the set temperature.

As the motor turns, it moves a plastic crank arm, which in turn moves a threaded, adjustable link rod connected to the temperature valve to obtain the correct blend of heated air from the heater and cooled air from the A/C evaporator.

The motor is the only replaceable component in the programmer.