Checking the function of the positioning motor for fresh/recirculated air flap -V154 and switch -E159 — AUDI

Notes:

To ensure that misted windows are de-misted as soon as possible, air recirculation mode will not operate with "air to windscreen". (Switch -E159 is released mechanically via the rotary control).
In air recirculation mode, the windows may become misty (the air humidity inside the vehicle increases and moisture condenses on the windows - the air is not dried as it is in vehicles with air conditioners).
Different types of the heater controls:

=> Parts List

For vehicles up to and including model year 2000 (only with switch -E159).
For vehicles as of model year 2001 (with switch -E159 and with switch for heated rear window).

Function of switch for heated rear window =>Page
80-13

Check function of switch -E159 and positioning motor -V154

Switch on ignition.
Set rotary switch -A- for fresh air blower -V2 to speed 3.
Turn rotary control -B- for air distribution to the "Air to dash panel vents" position.
Do not activate switch -C- for fresh/recirculation air flap -E159 (key with arrow; the illustration shows the type which were installed up to and including model year 2000).

Air is drawn in through the dust and pollen filter (fresh air mode - telltale in switch does not illuminate).

Actuate switch -C- (air recirculation mode - telltale in switch illuminates).

Air is drawn out of the passenger's footwell area (air recirculation mode).

Turn rotary control -B- for air distribution to end stop in the "Air to windscreen" position.

Telltale in switch -C- extinguishes, fresh/recirculated air flap moves to the "fresh air mode" position (-E159 is released via rotary control -B-).

Notes:

If the function is OK, but the windows mist up:
Check dust and pollen filter for dirt =>Page
80-35
Check forced air extraction =>Page
80-6
Check passenger compartment for the ingress of water.

If the function is NOK, check switch -E159.

Check function of switch -E159

Remove glove compartment.

=> Inner Body Assembly; Repair group 68
Inner Body Assembly

Detach connector -A- from positioning motor for fresh/recirculation air flap -V154.
Switch ignition on.
Turn rotary control for air distribution to the "Air to dash panel vents" position.
Switch -E159 is not actuated (not pressed).

Fresh air mode - telltale does not illuminate in switch.

Activate voltage tester V.A.G 1527 between contact 1 and 3 at connector -A- (between contact 2 and 3 in RHD vehicles).

Telltale in voltage tester illuminates.

Actuate switch -E159 (press).

Air recirculation mode - telltale illuminates in switch.
Telltale in voltage tester extinguishes.

Activate voltage tester between contacts 2 and 3 on connector -A- (between contacts 1 and 3 for RHD vehicles).

Telltale in voltage tester illuminates.

Turn rotary control for air distribution to end stop in the "Air to windscreen" position.

Telltale in switch and in voltage tester extinguishes.

Notes:

If no faults are determined during this test:
Check the freedom of movement of the fresh/recirculated air flap.
Replace positioning motor -V154.

If the function is NOK:
Check the wiring between -E159 and -V154 for open circuit or short circuit.
Check the power supply and earth connection to switch -E159.
Replace heater control.