Heating and Air Conditioning: Description and Operation

AIR CONDITIONING/RECIRC




The air conditioning compressor may be energized in any mode by depressing the A/C switch. This will cause the air passing through the evaporator core to be cooled and dehumidified.

When the Recirc button is depressed the recirc motor moves the air inlet valve from outside air to recirculated air position. In this position air from the passenger compartment is recirculated through the module. This function allows for maximum air conditioning performance. The use of Recirc in cold and damp or humid weather will cause the windows to fog up.



BI-LEVEL




When selecting the Bi-Level mode, air enters the moduic and passes through the evaporator core. Depending on temperature lever position some air may pass through the heater core. This air will then mix with the cooler air and then he discharged through the instrument panel and heater outlets. Air flow design eharacteristies of the module will divert most of this tempered air out of the instrument panel outlets, with the air from the heater outlet being slightly warmer.



VENT MODE




When Vent mode is selected, air enters the module. After flowing through the evaporator the air passes through the mode valve and out through the instrument panel outlets. The air maybe warmed by directing some or all to pass through the heater core by adjusting the temperature lever to the desired heat level.



HEATER MODE




When Heater mode is selected, with Recirc OFF, outside air enters the module and passes through the evaporator core. With A/C button OFF the air is no cooler or drier than when it entered.
When the temperature lever is moved from cold to hot, the temperature valve directs some or all of the air from the evaporator through the heater core, warming the air passing through it.
The mode valve closes and directs most of the warmed air to the lower and rear air outlets. A small amount of bleed air exits through the defroster ducts.

IMPORTANT: During extremely cold weather, -2O°F (-29°C) or colder, the engine's coolant temperature will decrease quickly when idling with the heater fan on high speed and cool air may flow from the heater outlets. The fan control switch should be set at a slower speed position (fan speed I or II) to maintain the hottest air flow.



DEFROST MODE




When the Defrost mode is selected, outside air enters the module and passes through the evaporator core. The air then passes through the heater core where it is heated. For maximum defrosting or in high humidity conditions do not engage the Recirc button. After the air passes through the heater core most of the air is directed through the mode valve to the defroster outlet. A small amount of bleed air will pass by the mode valve and out the lower air outlet The figure shows air flow with the temperature lever set to full hot.

IMPORTANT: Defrost/Defogging Windows: This setting directs the air through the windshield defroster outlets onto the windshield and past the front side windows. Use this setting if windows are fogged or icy. This setting will also help defog the front side windows. Set the control lever to defrost and set the temperature to full hot (far to the right). To quickly clear the windows, put the fan control switch to high and push the A/C button. (An indicator light will go on.)

NOTICE: To keep the glass fog free, the mode select lever should be positioned between Heater and Defrost. The Recirc button should be left off. The mode lever should be used to regulate air flow depending on driving conditions.