Vacuum System

Vacuum System

The flaps in the cabin air distribution vents and the water valve in the pipeline from the engine coolant system to the heater matrix are all operated by vacuum actuators. The vacuum for these is supplied by four solenoids mounted in pairs behind the front footwell outlets. Each solenoid and its associated pipe work is identified by a colour:

The vacuum supply pipes to the re-circulation and centre vent actuators are fitted with restrictors in order to slow down the operation of the flaps and avoid hunting. The re-circulation flaps can take up to 30 seconds to move to a new position.

Vacuum is piped to the solenoids from the engine manifold through a reservoir. The solenoids are energised by signals from the ECM in response to demand ,sensing and feedback signals.

Figure 1.

Key to Fig. 1

1. Vacuum reservoir
2. Defrost solenoid
3. Defrost-demist actuator
4. Restrictors
5. Centre vent solenoid
6. Centre vent actuator
7. Defrost vacuum pipe
8. Centre vent vacuum pipe
9. Recirc. solenoid
10. Recirc actuator
11. Recirc. vacuum pipe
12. Water valve solenoid
13. Water valve actuator
14. Water valve vacuum pipe

Figure 2.

Key to Fig. 2

1. Defrost (Green) solenoid
2. +12V Defrost input from ECM pin 12
3. Defrost output to ECM Pin 11
4. Recirc (Blue) solenoid
5. +12V Recirc. input from ECM Pin 3
6. Water valve (Red) solenoid
7. +12V Water valve input from ECM Pin 17
8. Centre vent (Black) solenoid.
9. +12V Centre vent input from ECM Pin 18
10. ECM earth-ground