Push-Button Switch Replacement

The vacuum portion of this switch controls the operation of the water valve and positions all doors in the unit except the blend air door. The electrical portion of the switch controls the A/C compressor, blower motor and the electronic servo-motor operation.

When the switch is in the OFF position, the inlet air door is closed to outside air, the mode door is in the A/C position, the Heat-Defrost door is in the HEAT position, and the heater core coolant flow is OFF. No air flows through the unit and the compressor and SATC electronics are OFF, since the blower and compressor clutch circuits are open.

When the switch is in the MAX A/C position, all doors are in the same position as in the OFF position. The electrical circuits to the blower motor, compressor clutch and the SATC electronics are closed. This mode is recommended for initial cool down, extreme outside humidity, or high ambient temperatures. Only High and Medium 2 (M2) blower speeds will operate with no automatic temperature control in this mode.

The NORM position can be used when the vehicle has been cooled to the desired temperature. The vacuum application at the outside recirculating air door actuator is transferred to the rod side, moving the door away from the outside-air inlet and closing the recirculating inlet. The water valve is open and all other vacuum applications and door positions are the same as the MAX A/C position. The blower motor and compressor are on. In this position, a VENT mode can be obtained by first pushing the NORM button and then pulling it back out. This will open the clutch circuit and allow the blower motor to force outside air into the passenger compartment.

In BI-LEVEL (A/C Vent) position, outside air enters the vehicle and is directed through 2 levels of air outlets: the upper level (A/C outlets and lap coolers) and the lower level (heater outlets and defroster bleed). All four blower speeds are operational and the compressor is on. When the button is pulled out all the way, the compressor goes off, providing a vent position. Interior comfort is obtained with a split in airflow and temperatures, meaning that a temperature difference exists between the two levels. Since the upper level is cooler than the lower level, increased comfort is available during a cold and sunny day.

In the HEAT position, outside air door is open as in the A/C position. Vacuum is applied to the Bi-Level door actuator, closing off the passage to the air conditioning distribution duct and opening the passage to the heater-defroster duct. Since the heater-defroster door is in the heat position, the full flow of heated air is routed through the heater outlets, except for a small amount that bleeds through the defroster outlets. The water valve is open, the blower switch is activated and the compressor is off.

In the DEFROST position, all conditions are the same as for heater operation, except that no vacuum is applied to defroster door actuator which is spring loaded toward the defrost position. The recirculating air door will be open to outside air and the defroster door will be open. There will be a small amount of heat through the heater outlets, and the compressor will be operating. Compressor operation can be eliminated in the Defrost position by pulling the DEFROST button fully out. This procedure should be used only in cold weather below 32 °F. All other defroster operations will continue with button in either position.