Front Mode Controls

The front air delivery or ventilation controls are operated by vacuum. There are four vacuum actuators which direct the flow of air in the vehicle. Each actuator is spring loaded for a normal position but when vacuum is applied, the actuator moves to another position. This moves the air delivery valve or door and changes the air flow path. When vacuum is removed, the actuator returns to the normal position.

The Air Inlet Valve (or recirculation door) selects the source of the incoming air. It is a two position valve which either directs outside air into the vehicle or recirculates the inside air. In it's normal position A, it directs outside air into the vehicle. The Air Inlet Valve is operated by the Air Inlet Valve Actuator. Vacuum is aligned to the Air Inlet Valve Actuator from the Heater and A/C Controller through the ORN vacuum tube. Vacuum is supplied when the controller's Mode Switch is in the MAX A/C position. The actuator then moves the valve to the B position which recirculates internal air. With the Mode Switch in any other position, the Air Inlet Valve is in the outside air position.

The Outer Mode Valve (or A/C door) and the Inner and Outer Mode Valve (or slave door) direct the flow of the circulating air either through the I/P Outlets or to the Defroster Valve. When the engine is running and the Mode Switch in the OFF position, the valves are normally aligned to direct air flow to the Defroster Valve. The Heater and A/C Controller's Mode Switch normally isolates vacuum from the Outer Mode Valve Actuator. However, it normally applies vacuum to the Inner and Outer Mode Valve Actuator through the BRN vacuum tube. The vacuum positions the Inner and Outer Mode Valve in the A position. Since no vacuum is applied to the Outer Mode Valve Actuator, the Outer Mode Valve remains in the A position.

In the MAX A/C, A/C, and Vent modes, air flow is directed through the I/P outlets. With these Mode Switch selections, vacuum is applied to the Outer Mode Valve Actuator through the YEL vacuum tube. This positions the Outer Mode Valve in the B position. Also, in these mode selections, vacuum is removed from the Inner and Outer Mode Valve Actuator. This positions the Inner and Outer Mode Valve the B position. Most air flow is directed through the I/P Outlets.

When Bi-Level is selected on the Mode Switch, vacuum is removed from the Outer Mode Valve Actuator. The Outer Mode Valve then moves to the A position. Vacuum remains isolated from the Inner and Outer Mode Valve Actuator and this valve remains in the B position. This alignment allows increased air flow to the Defroster Valve.

The Defroster Valve (or defrost/heater door) directs air flow either through the defroster vents when in the A position, through the heater vents when in the C Position, or though both the defroster and heater vents when in the B Position. When the Mode Switch is placed in the OFF, MAX A/C, A/C, Vent, or Heat positions, vacuum is applied through the RED vacuum tube to the bi-directional Defroster Valve Actuator. This moves the Defroster Valve to Position C which directs air flow through the heater vents. With the Mode Switch in the Defrost position, vacuum is applied to the other side of the hi-directional Defroster Valve Actuator through the BLU vacuum tube. This positions the Defroster Valve in the A position. Air is then routed to the defroster vents. With the mode switch in either the Blend or Bi-Level positions, no vacuum is applied to the actuator and it returns to the B position. Air is routed in both directions.