Operating Modes

With the automatic (C68) system the driver can manually select seven different modes of operation from the heater and A/C control. The dual zone (CJ2) system has eight modes available. The heater and A/C programmer can also access three additional purge modes when certain conditions exists.

Off

When the off mode is selected the blower motor will be running at its minimum calibrated speed and A/C compressor will be turned OFF.

The heater and A/C programmer will allow all vacuum actuators to vent. The air inlet valve is in the outside air position; the heater-A/C-bi-level valve vacuum actuator is in the bi-level position and the defrost-A/C valve vacuum actuator is in the defrost position.

When the vehicle is moving, air flowing over the vehicle increases air pressure just ahead of the windshield so some air is forced into the outside air inlet, through the heater and A/C module assembly and out the floor and windshield outlets.

Temperature control circuitry is still activated so that heater and A/C programmer operates the air mix valve and attempts to match inside temperature and SET temperature. Since the compressor is not running, however, system air can be warmed, but not cooled.

Auto

When the auto mode is selected, the programmer will turn on the AUTO and SET temp indicators. The blower indicators will be turned off indicating auto control. The driver can override auto blower control by turning the fan speed knob.

The heater and A/C programmer evaluates information supplied by the heater and A/C control and its network of sensors and determines whether A/C, BI-LEVEL, DEFOG or HEAT mode is required. The programmer then energizes the appropriate solenoid(s) to enter this mode.

Information supplied to the programmer also determines whether outside air is drawn into the system (NORM A/C mode) or inside air is recirculated (MAX A/C mode).

The heater and A/C programmer determines the proper air discharge temperatures and powers the air mix valve actuators to move the air mix valves to the proper position.

Defog

When defog mode is selected the blower motor is turned ON and blower speed can be manually adjusted by turning the fan speed knob. The A/C LED is illuminated and the compressor is activated if outside temperature is above 8°C (48°F) and runs to keep the evaporator core at about 1°C (33°F).

The heater and A/C programmer will allow all vacuum actuators to vent the same as in off mode. air inlet valve is in the outside air position; the heater-A/C-hi-level valve is in the bi-level position and the defrost-A/C valve is in the defrost position.

Outside air is pulled into the system by the blower, the air its cooled and dehumidified, then heated as necessary, and forced out the floor and windshield defroster outlets. The heater and A/C programmer determines the proper air discharge temperatures and positions the air mix valves accordingly.

Bi-Level

When bi-level mode is selected the blower motor is turned ON and blower speed can be manually adjusted by turning the fan speed knob.

The heater and A/C programmer will apply vacuum to the defrost-A/C valve vacuum actuator only, all other actuators are venting:

- Outside air-recirc valve is in the outside air position.
- Defrost-A/C valve is in the A/C position.
- Heater-A/C-bi-level valve is in the bi-level position.

Outside air is pulled into the system by the blower. If A/C is selected, the air is cooled and dehumidified, then heated as necessary, and forced out the instrument panel and floor outlets.

The heater and A/C programmer determines the proper air discharge temperatures and positions the air mix valves accordingly.

Recirc

When RECIRC mode is selected, the programmer allows vacuum to be applied to the O/S air recirc valve actuator which positions the O/S air recirc valve in the recirculate position.

Recirc mode is available for operation in UPPER, LOWER and BI-LEVEL modes. RECIRC is not allowed during DEFOG or FRONT DEFROST modes as this could cause windshield fogging.

The RECIRC function will operate for approximately ten minutes before it times out (shuts off). Additional activation can be made after time out. While RECIRC is operational any manual mode changes or ignition cycles will cancel the function, and allow outside air into the system.

Front Defrost

When front defrost mode is selected the blower motor is turned ON and blower speed can be manually adjusted by turning the fan speed knob. The A/C LED is illuminated and the compressor is activated if outside temperature is above 8°C (48°F) and runs to keep the evaporator core at about 1°C (33°F).

The heater and A/C programmer applies vacuum to one side of the heater-A/C-bi-level valve vacuum actuator, all other actuators are venting; the air inlet valve is in the outside air position; the defrost-A/C valve is in the defrost position and the heater-A/C-bi-level valve is in the A/C position.

Outside air is pulled into the system by the blower, the air is cooled, dehumidified, heated, then released out the defroster outlets.

The heater and A/C programmer determines the proper air discharge temperatures and positions the air mix valves accordingly.

Upper

When upper mode is selected the blower motor turns ON and blower speed can be manually adjusted by turning the fan speed knob.

The heater and A/C programmer applies vacuum to the defrost A/C valve vacuum actuator and one side of the heater-A/C-bi-level valve; the air inlet valve is in the outside air position; the defrost-A/C valve is in the A/C position and the heater-A/C-bi-level valve is in the A/C position.

Outside air is pulled into the system by the blower, if A/C is selected the air is cooled and dehumidified, then heated as necessary, and forced out the instrument panel outlets.

The heater and A/C programmer determines the proper air discharge temperatures and positions the air mix valves accordingly.

Lower (Oldsmobile)

When lower mode is selected, blower motor circuitry is turned ON and blower speed can be adjusted using the fan speed knob. The A/C compressor can be activated by pressing the A/C button. If outside temperature is above 7.2°-10°C (45°-50°F), the A/C runs to keep the evaporator core at about 1°C (33°F).

Vacuum is applied to one side of the heater-A/C-bi-level valve vacuum actuator. All other actuators are venting; the air inlet valve is in the outside air position; the defrost-A/C valve is in the defrost position and the heater-A/C-bi-level valve is in the heater position.

Outside air is pulled into the system by the blower, if A/C is selected the air is cooled and dehumidified, then heated as necessary, and forced out the floor outlets.

The heater and A/C programmer determines the proper air discharge temperatures and positions the air mix valves accordingly.

When dual zone mode is selected, either by pressing the PASS button or adjusting the passenger control head. The programmer operates the driver and passenger air mix valves independently. If the passenger operates the passenger temperature control knob to request a warmer or cooler temperature on that side of the vehicle, the programmer operates the passenger air mix valve actuator to increase or decrease passenger side discharge temperature.

Rear Defogger and Heated Mirror(s)

With the ignition switch in RUN, voltage is supplied to the rear defogger relay coil. Pressing the rear defogger switch signals the heater and A/C programmer (CJ2 and 68) or beater and A/C control assembly (C61 and C67) to provide a ground path for the rear defogger relay coil. The relay energizes, closing the contact and applying voltage to the rear defogger and heated mirror(s), if equipped. The rear window and outside mirror(s) become warm to remove condensation from the glass surfaces.

The first time the rear defogger switch is pressed, the solid state timer allows the rear defogger and heated mirror(s) to operate for approximately ten minutes. Each time the rear defogger switch is pressed thereafter, the solid state timer resets to operate for five minutes when the ignition switch is turned OFF then back to RUN. The timer also shuts off when the rear defogger control switch is pressed while the rear defogger and heated mirror(s) are already on.

Defogger grid repair can be found in Stationary Windows.