Control Assembly: Description and Operation

The control assembly consists of three main parts:

System Airflow Schematic And Vacuum Control Chart:

1. The function selector vacuum valve which is combined with three internal electrical switches.
a. The electro vacuum selector valve directs source vacuum to various vacuum motors and connects the vacuum from the thermal blower lockout switch relay to the outside air-recirculate door in the FLOOR position.
b. Three single-pole electrical switches control the electrical supply to the A/C clutch and the Automatic Temperature Control (ATC) module.
2. A blower switch that provides continuous variable blower speeds from LO to HI and a detented AUTO position. This is accomplished by a microprocessor board which, based on information from the ambient and the in-car temperature sensors, positions the blend door and controls the speed of the blower automatically, when in the AUTO position or variably from LO to HI by vehicle operator selection. When the electro vacuum selector valve is in the FLOOR position, the on/off operation of the ATC control module is controlled by the Thermal Blower Lockout (TBL) switch.
3. The temperature control swhich provides input to the ATC module.