Control Assembly: Description and Operation

A/C Controller:

CONTROL ASSEMBLY
The operation of the A/C system is controlled by the buttons and the lever on the control assembly. The compressor clutch and blower are connected electrically to the control assembly wiring harness. The blower circuit is open in the "OFF" mode and airflow is provided by the four blower speeds available in the remaining modes. Cooled and dehumidified air is available in the Max, Normal, Bi-level, Defog, and Defrost modes.

Mode Selection
The temperature lever controls the temperature valve through a potentiometer in the control and electric motor attached to the heater module. The modes of operation are controlled by pushbuttons that send an appropriate electrical signal to the five solenoid valves that control the flow of vacuum on the various vacuum valve positioning actuators. The blower is turned off in the "OFF" mode operation. Temperature valve position is independent of mode selection.

Modes Of Operation
The flow of air from the heater system during the various modes of operations is as follows:
^ "OFF" -Floor outlet, forced outside air only
^ Max -Instrument panel outlets, recirculated air
^ Normal -Instrument panel outlets, outside air
^ Bi-level -Instrument panel and floor out-lets, outside air
^ Heater -Floor outlets and small amount through defroster outlets, outside air
^ Defog -Defroster and floor outlets, outside air
^ Defrost -Defroster outlets, outside air

Engine Cooling Fan
The electrical engine cooling fan on some cars is not part of the A/C system; however, the fan is operational any time the A/C control is in Max, Normal, Bi-level, Defog, or Defrost modes or, is controlled by the head pressure control switch. The operation of the cooling fan is controlled by the Electronic Control Module (ECM) through the cooling fan relay.

Complete wiring diagrams are located under Diagrams and diagnosis for the A/C Electrical System is located under Testing and Inspection.