Vacuum Controller: Description and Operation

Fig.5 A/C Vacuum Line:

Only models with the optional heater-A/C system have a vacuum control system. This system uses engine vacuum to operate the recirculation air door. The vacuum control system includes the following components:

- Vacuum harness - The vacuum harness is plastic tubing that carries engine vacuum from the source vacuum port in the engine compartment to the various other components of the system.
- Check valve - A one-way vacuum check valve is installed in the vacuum harness between the source vacuum port in the engine compartment and the heater-A/C control.
- Switch - A vacuum switch is integral to the heater-A/C control on the instrument panel.
- Actuator - A vacuum actuator is mounted to the outside of the heater-A/C unit housing near the recirculation air door.

Fig.7 Recirculation Air Door Vacuum Actuator:

When engine vacuum is supplied to the actuator, the actuator linkage moves the recirculation air door to the recirculation-air position. The actuator is spring loaded so that the recirculation air door moves to the default outside-air position when there is no vacuum supplied. Vacuum is switched to the actuator by placing the air flow control knob in the Recirculation position. The mode and the air flow control are mechanically interlocked so that the air flow control cannot be placed in the Recirculation position if the mode control knob is in or between the Mix and Defrost positions. The check valve prevents the vacuum in the vacuum control system from being depleted during low engine vacuum operating conditions.