Circuit Operation (Air Delivery)

CIRCUIT OPERATION
(AIR DELIVERY)
ELECTRONIC A/C CONTROL ASSEMBLY
With the Ignition Switch in "RUN," voltage is applied through Fuse 6 to the Electronic A/C Control Assembly. The operating mode of the system is determined by buttons on the front panel. Ground signals determine which air valves are to be operated as well as the position of the Temperature Valve.

SOLENOID MODULE
The Solenoid Module contains the solenoid valves that control the vacuum actuators. When the solenoids are de-energized, the valves vent the vacuum actuators, allowing the vacuum actuator to return to the Vent position.

RECIRCULATION VALVE
The Recirculation Valve closes off most of the outside air inlet so that the air from the inside of the vehicle is recirculated through the A/C System for maximum cooling. The outside air inlet is partially closed when vacuum is applied to the actuator. When the vacuum actuator is vented, the Recirculation Valves close off the in-car air inlet which allows outside air to be drawn into the vehicle.

TEMPERATURE VALVE
The Temperature Valve determines how much air flows through the Heater Core, which determines the temperature of the air to the outlets. It is moved by the Air Mix Door Motor. The position of the valve is determined by the temperature selected at the Electronic A/C Control Assembly.

DEF/HEATER
The DEF/Heater Valve determines whether air flow will be directed to the windshield defrost outlets. With no vacuum applied to the actuator, the valve is positioned to allow air flow to the windshield defrost outlets, with some bleed to the heater outlet.

UPPER/LOWER MODE
The Upper/Lower Mode Valve can assume three positions and is operated by a bi-directional vacuum actuator which can move the valve to either of two positions. If no vacuum is applied to either vacuum actuator, the valve is in midposition. Air flow with the valve in midposition will be delivered to the panel outlets and the floor outlets (Bi-Level).


When the Upper/Lower Solenoid (# 3) (tan vacuum hose) is operated, the valve is positioned to direct air flow to the A/C outlets. When the Upper/Lower Solenoid (# 4) (red vacuum hose) is operated, the valve is positioned to direct air flow to the heater outlets and defroster outlets.

HEATER WATER VALVE
(1991 AND 1992 EARLY PRODUCTION)
The Heater Water Valve determines whether water will flow through the Heater Core or not. When the Heater Water Valve Vacuum Actuator is operated, the Heater Water Valve will close, stopping water flow into the Heater Core.

HEATER SHUT OFF AIR VALVE
(1992 LATE PRODUCTION)
The Heater Shut off Air Valve is used to block any air attempting to exit the Heater Core when temperature control is set to 16~C (60~-65~), provided that program number in index number "01" is 0-56 (program number range is 0-255). Otherwise, it rotates out of the way so as not to block any air flow.