Fresh Air Door Motor -V438- 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 the cover over fresh air intake. Refer to FRESH AIR INTAKE, REMOVING AND INSTALLING ).
- For back pressure regulation, the fresh air intake channel is partially closed via the back pressure door when at high speeds (from approximately 80 km/h) by the Front A/C Display Control Head -E87- (the position of the air recirculation door is specified by the Front A/C Display Control Head -E87-).
- To reduce the change in noise from the Fresh Air Blower -V2- due to the different air intake when switching from fresh air to recirculating air mode or vice versa, activate the Fresh Air Door Motor -V438- and the Recirculation Door Motor -V133- as follows:
-- When switching from fresh air to recirculating air mode, the air recirculation door is opened first, then the fresh air intake duct is closed via the back pressure/fresh air door.
-- When switching from recirculating to fresh air mode, the fresh air intake duct is first opened via the back pressure/fresh air door, then the air recirculation door is closed.
-- In partial recirculation mode, the air recirculation door opens and the back pressure/fresh air door is brought into a center position by the Front A/C Display Control Head -E87- (the fresh air and recirculation air intake duct are opened slightly at the same time). This achieves improved cool-off in certain temperature ranges and simultaneously draws in a certain portion of fresh air as well.