Operating Modes

Mode Operations:

The driver can select from eight different modes of operation from the heater A/C control. The heater A/C control can initiate two additional purge and delay modes when certain conditions exist.

Off

When the Off mode is selected the blower motor and A/C compressor will be turned off. The heater A/C control will not apply vacuum to any vacuum actuators this would allow ram air to travel to all outlets/vents. 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 blower case and out all of the outlets/vents this is called ram air.

Temperature control circuitry is still activated so that the heater A/C control operates the air mix valves and attempts to match in-vehicle 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 control will turn on the Auto and Set temperature indicators. The blower indicator will be turned off indicating auto control. The driver can override auto blower control by pressing the fan speed button.

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

Information supplied to the heater A/C control also determines whether outside air is drawn into the system or inside air is recirculated.

A/C

When A/C mode is selected the heater A/C Control illuminates the A/C LED. The compressor is activated if ambient temperature is above 3°C (38°F) and runs to keep the evaporator core at about 3°C (38°F). A/C compressor is automatically commanded in Front Defrost and Defog mode.

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

Mode

The Mode button will operate the following controls Defog. Bi-Level, Upper, and Lower when selected on the control head. The LED will also display what mode has been selected, as shown.

Defog

When Defog mode is selected the blower motor is turned ON and blower speed can be manually adjusted by pressing the fan speed button. The A/C LED is illuminated and the compressor is activated if ambient temperature is above 3°C (38°F) and runs to keep the evaporator core at about 3°C (38°F).

The A/C valve closes and the heater/defroster door is in a mid position allowing air to travel to the defroster outlets, and floor outlets known as defog mode. The outside air recirc valve is in the outside air position.

Outside air is pulled into the system by the blower, the air is cooled and dehumidified, then heated as necessary, and forced out the floor and windshield defroster outlets. The heater A/C Control 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 pressing the fan speed button.

The heater A/C Control will vent the A/C vacuum actuator and vacuum is applied to the heater-defroster actuator. The A/C valve is in the bi-level position. The heater-defroster valve is in the closed position. The outside air-recirc valve is in the outside air 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 A/C control 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 pressing the fan speed button.

The heater A/C control applies vacuum to the A/C bi-level valve. The outside air-recirc valve is in the outside air position. The A/C 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.

Lower

When Lower mode is selected the blower motor is turned on and blower speed can be manually adjusted by pressing the fan speed button.

The heater A/C control will apply vacuum to the heater-defroster actuator valve. The A/C bi-level valve closes and allows air to travel to the heater-defroster valve. The heater-defroster valve will be in the heater mode position. The outside air-recirc valve is in the outside air position.

Recirc

When Recirc mode is selected, the inlet air to the module is drawn from the vehicle's interior rather than from outside of the vehicle. This mode is used for maximum air cooling and dehumidification.

Recirc mode is available for operation in Upper, Lower, Defog, and Bi-Level modes. Recirc is not allowed during Front Defrost mode because this could cause windshield fogging.

The recirc function will be canceled upon a transition from automatic mode to manual mode and upon a transition from manual mode to automatic mode, unless the microprocessor requests recirc based on sensor inputs.

Front Defrost

When Front Defrost mode is selected the blower motor is turned ON and blower speed can be manually adjusted by pressing the fan speed button. The A/C LED is illuminated and the compressor is activated if ambient temperature is above 3°C (38°F) and runs to keep the evaporator core at about 3°C (38°F).

The heater A/C control applies vacuum to the heater/defroster valve vacuum actuator, the outside air-recirc valve is in the outside air position; the A/C valve is closed.

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

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

Rear Defog

Pressing the Rear Defog button will cause the LED in the switch to illuminate. The first operation of the button will allow the rear defog to operate for 10 minutes and the second and consecutive operations will allow operation for only 5 minutes. Any activation's while the rear defog LED is 'it will cause the rear defog operation to be turned off.