Back Pressure Door Motor (V71), Function

Back Pressure Door Motor (V71), Function

• 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. Refer to => [ Fresh Air Intake ] Fresh Air Intake).

• For air flow regulation, fresh air intake channel is closed partially via air flow door at high vehicle speed (from approximately 80 km/h (50 mph)) by A/C control head Climatronic Control Module (J255) (position of recirculating air door is specified by 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, then the fresh air intake channel is closed via the back pressure and 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 partially recirculating air mode, recirculating air door - E - is opened and back pressure- / fresh air flow door is brought into an intermediate position by Climatronic control module (fresh air and recirculating air intake channel are slightly opened simultaneously). This achieves improved cool-off in certain temperature ranges and simultaneously draws in a certain portion of fresh air as well.