Checking For Leaks on Fresh Air/Recirculated Air Flap

Checking For Leaks on Fresh Air/Recirculated Air Flap






Check valve (31)
Check for leaks, section a.

Tests b to d
Prepare.

Vacuum circuit 1, switch-over valve (Y13) and air volume switch (S3)
Check for leaks, section b, at blower stage 1 and with fresh/recirculated air switch off.


Vacuum circuit 2, vacuum element for fresh air/recirculated air flap (33), long stroke
Check for leaks, section c, at blower stage 1 and with fresh/recirculated air switch on.

Vacuum circuit 3, vacuum element for fresh air/recirculated air flap (33), long and short strokes
Check for leaks, section d, at blower stage 0.

Permissible leakage
Permissible leakage per vacuum circuit 30 mbar/min at 400 mbar vacuum
(without vacuum supply tank)

Permissible leakage of check valve 50 mbar in 10 mm
at 300 mbar vacuum

Permissible leakage of other components 20 mbar/min at 300 mbar vacuum








Special tool


Self-made tool
1 blind plug 000 987 11 45


a) Checking check valve (31) for leaks







1 Disconnect green/red vacuum line and dark red/green vacuum line from check valve (31).
2 Connect tester (arrow) to check valve. Seal off second connection with blind plug.
3 Evacuate with tester and read pressure gauge. If pressure rises, renew check valve.


Preparing for tests b to d







1 Disconnect green/red vacuum line and dark red/green vacuum line from check valve (31).
2 Switch on ignition.


NOTE: The tester remains connected to the green red vacuum line for the entire duration of the test.


b) Checking vacuum Circuit 1, switch-over valve (Y13) and air volume switch (S3) for leaks
1 Move air volume switch to stage 1.
2 Evacuate with tester (approx. 400 mbar) and read pressure gauge.
3 If the indicated pressure changes. check the switch-over valve for the fresh air/recirculated air flap (Y13), the inner connection of the air volume switch (S3) and the middle green/red vacuum lines. and renew if necessary.





Vacuum circuit 1, air volume switch at stage 1 and fresh/recirculated air switch off
S3 Air volume switch
Y13 Switch-over valve fresh air/recirculated air flap
33 Vacuum element for fresh air/recirculated air flap





c) Checking vacuum circuit 2, vacuum elements for fresh air/recirculated air flap (33, long stroke) for leaks
1 Switch on fresh/recirculated air switch.
2 Evacuate with tester (approx. 400 mbar) and read pressure gauge.
3 If the indicated pressure changes, check vacuum elements (33) and renew if necessary Service and Repair or check vacuum lines from switch-over valve (side connection) to vacuum element and renew if necessary.





Vacuum circuit 2, air volume switch at stage 1 and fresh recirculated air switch on
33 Vacuum element for fresh air/recirculated air flap



d) Checking vacuum circuit 3, vacuum elements for fresh air/recirculated air flap (33, long and short strokes) for leaks
1 Move air volume switch to "0".
2 Evacuate with tester (approx. 400 mbar) and read pressure gauge.
3 If the indicated pressure changes, check vacuum elements (33) and renew if necessary Service and Repair or check vacuum lines from switch-over valve (side connection) to vacuum element and renew if necessary.





Vacuum circuit 3, air volume switch at "0"
33 Vacuum element for fresh air/recirculated air flap