A/C System - Manual

CONSTRUCTION
The A/C-Heater System contains an A/C-Heater Function Selector Switch and Vacuum Valve, a Temperature Control Lever (on the control assembly), a blower housing assembly, an evaporator assembly and ductwork (behind the instrument panel), and a Compressor and Condenser (in the engine compartment).

OPERATION
Function Selector and Vacuum Valve
The Function Selector and Vacuum Valve operate together to control system vacuum and electrical operation. vacuum motors operate doors to direct air flow. The Function Selector Switch connects power to the Blower Motor and to the A/C Clutch Coil circuit.

A/C Clutch Cycling Pressure Switch
The A/C Clutch Cycling Pressure Switch cuts off power to the A/C Clutch Coil when the suction pressure drops below approximately 26 PSI. The switch will close to resume A/C operation when system pressure rises to between 40 and 47 PSI.

Power to the A/C Clutch Coil is controlled through a Wide Open Throttle (WOT) Relay. The WOT Relay is controlled by the Powertrain Control Module (PCM) and turns off the A/C System during certain engine operating conditions. The A/C cut-out conditions include wide open throttle, high engine coolant temperature, low engine idle speed, high engine speed, an engine start up. The WOT A/C Cutout Relay is energized by the PCM and opens the clutch circuit during these conditions.

Temperature Control Lever
The Temperature Control Lever moves a control cable connected to the Temperature Blend Door, which directs air through and around the Heater Core to obtain the desired air temperature.

Lever Position and Operation
OFF
Vacuum is applied to the Outside-Recirculate Door Vacuum Motor, closing that door to outside air. Vacuum is applied to both ports of the Floor-Defrost Door Vacuum Motor to open the floor outlet. The blower does not operate, and no air passes through the system.

MAX A/C (Recirc)
The Outside-Recirculate Door closes to outside air. The Floor-Defrost Door closes the floor outlets (no vacuum on motor), and vacuum is applied to the Panel-Defrost Door to send air to the instrument panel registers.

NORM A/C (Outside Air)
Outside air comes through the Outside-Recirculate Door. the Panel Door sends air to the instrument panel registers. the Temperature blend door (controlled by a cable) directs air flow through and/or around the Heater Core.

Vent
Air flow is the same as for the NORM A/C operation. The compressor is OFF.

DEF/FLR
The Floor-Defrost Door is at mid-position and there is no vacuum at the Panel Door so air is split between the windshield outlets and the floor ducts. The compressor is on.

FLOOR
The Floor-Defrost Door is at full floor position (vacuum at both ports) and air is sent only to the floor. A small flow of air bypasses to the Floor-Defrost Door and is directed to the defroster outlets by Panel-Defrost Door (no vacuum).

DEFROST
No vacuum is applied to the vacuum motors. Air flow is directed to the plenum by the Floor-Panel Door and to the windshield defrost outlets by the Panel-Defrost Door.