Back Pressure Door Motor

Back Pressure Door Motor

• The position of the fresh air- and back pressure door is visible via the air intake opening in the plenum chamber when the air recirculation is closed (if necessary, remove the plenum chamber cover and cover over fresh air intake => [ Fresh Air Intake ] Service and Repair).

• For air flow regulation, the fresh air intake channel is closed partially via the back pressure door at a high vehicle speed (from approximately 80 km/h (50 mph))by the Climatronic control module (J255) (the position of the recirculation door is specified by the Climatronic control module).

• To reduce the change in noise from the fresh air blower (V2) due to different air intake when switching from fresh air to recirculation or vice versa, the back pressure door motor and recirculation door motor (V113) are activated as follows:

- When switching from fresh air to recirculation mode, the recirculation door is first opened. The fresh air intake channel is then closed via the back pressure/fresh air door.

- When switching from recirculation to fresh air mode, the fresh air intake channel is first closed by the back pressure/fresh air door, then the recirculation door is closed.

- In partial recirculation mode, the recirculation door is opened and the back pressure/fresh air door is moved by the Climatronic control module to a center position (the fresh air and recirculating air intake channel are opened slightly simultaneously). This achieves improved cool-off in certain temperature ranges and simultaneously draws in a certain portion of fresh air as well.