Manual Electronic Controls

System Block Diagram:

GENERAL INFORMATION
The electronic air conditioning system (C67) is an electronically controlled heating, ventilating and air conditioning system. The driver may select from eight different operation modes, plus activate the rear defogger from the system control panel. Blower speed and outlet air temperature are also manually adjustable from the control panel.

The electronic air conditioning system uses a cycling clutch orifice tube (CCOT) type refrigeration system.

SYSTEM COMPONENTS

Heater And A/C Control Assembly
The electronic heater and A/C control assembly is the vehicle operator's control point for the electronic air conditioning system. The heater and A/C control assembly Includes soft-touch buttons for the various system operating modes (OFF, MAX A/C, NORM A/C, BI-LEVEL. VENT, HEATER, DEFOG, DEFROST), a blower speed control lever, and a temperature control lever. Vehicles equipped with a rear window defogger also have the system's ON/OFF switch located in the heater and A/C control assembly. Each operating mode button contains an LED indicator that illuminates when selected. The rear window defogger button also contains an LED indicator.

The heater and A/C control assembly is the electronic air conditioning system's "brain"; It sends commands to system components that control A/C compressor operation, air discharge location, air discharge temperature and blower operation.

A/C Solenoid Switch Assembly
The A/C solenoid switch assembly operates vacuum actuators to control air intake and discharge locations. Inside the A/C solenoid switch assembly are 4 solenoid-actuated vacuum valves that respond to heater and A/C control assembly electrical signals. The vacuum valves, in turn, vent or apply vacuum to the vacuum actuators. By energizing various solenoid-actuated vacuum valve combinations, the heater and A/C control assembly can control whether air comes out the floor outlets, panel outlets or defroster outlets. It also determines whether fresh (outside) air is drawn into the system or inside air is recirculated.

Heater And A/C Module
The heater A/C module is where all system air is heated, cooled, mixed together, and directed to the various air ducts and outlets. The module consists of a housing with inlet openings, outlet openings, air passages and air valves. Vacuum actuators and an electric motor (mounted on the housing) operate the air valves according to A/C solenoid switch assembly signals.

Blower Speed Relay
When energized by the heater and A/C control assembly, the blower speed relay applies voltage to both the blower switch (in the heater and A/C control assembly) and the blower resistors to enable the blower motor.

Blower Switch
The blower switch, mounted in the heater and A/C control assembly, controls blower speed. Blower switch lever position determines whether current flows to the blower resistors or the high speed blower relay.

Blower Resistors
The blower resistors comprise an assembly which contains 3 separate resistors. Blower speed is regulated by routing current through none, 1, 2 or all 3 resistors. The blower switch position (in the heater and A/C control assembly) determines how many resistors are bypassed.

High Speed Blower Relay
When energized by the blower switch, the high speed blower relay allows current to flow directly from the RH underhood fuse block to the blower motor. With all blower resistors bypassed, the blower motor runs at high speed.

Blower Motor
The blower motor is a DC motor whose speed is proportional to input voltage. With low voltage applied to the motor, it runs at low speed; with high voltage applied to the motor, it runs at high speed. The blower switch (in the heater and A/C control assembly) determines how much voltage is applied to the blower motor.

A/C Temperature Valve Actuator
The A/C temperature valve actuator follows commands from the temperature lever in the heater and A/C control assembly to control outlet air temperature. A reversible DC motor in the actuator operates the air mix valve, which blends cooled and heated air inside the heater and A/C module.

Vacuum Actuators
The vacuum actuators are vacuum servos that operate valves inside the heater and A/C module. Valve position determines whether air comes out the floor outlets, panel outlets or defroster outlets. It also determines whether fresh (outside) air is drawn into the system or inside air is recirculated. Three actuators are used: two single-diaphragm actuators and one double-diaphragm actuator. The vacuum actuators are mounted on the heater and A/C module and are connected to the A/C solenoid switch assembly by vacuum hoses.