Preparatory Information

Checking flap control vacuum system for leaks





Check valve (36) and vacuum reservoir (37, except diesel)
Check for leaks, section A

Test B to E
Prepare (see below)

Vacuum circuit 1, valve block (Y7)
Check for leaks, section B with function selection "Defrost"

Vacuum circuit 2, vacuum element for fresh/recirculated air flap (42)
Check for leaks, section C with function selection "O"

Vacuum circuit 3, vacuum element for footwell flaps (39)
Check for leaks, section D with function selection "Upper/Lower Vents" and selector wheel "MAX"

Vacuum circuit 4, vacuum element for center nozzle flap (40) for diverter air flap (41) and for defroster nozzle flaps (38)
Check for leaks, section E with function selection "Lower Vents" and selector wheel "MIN"


Permissible leakage rate
- Permissible leakage rate per vacuum circuit (without vacuum reservoir) -- 30 mbar/min at 400 mbar vacuum
- Permissible leakage rate of the check valve -- 50 mbar in 10 minutes with 300 mbar vacuum
- Permissible leakage rate of the remaining components -- 20 mbar/min with 300 mbar vacuum

Special tool




Self-made tool
1 plug 000 987 11 45

Note: The vacuum test has been divided into 5 test circuits (A to E). If a certain fault is experienced (e.g. footwell flaps fail to open), the appropriate circuit can be checked first.

If a leak is suspected in the entire vacuum system for the automatic climate control, the test should commence with step "A" and continue with the other test circuits until the faulty vacuum circuit has been found.


Preparing test B to E




1 Pull vacuum line medium green/yellow off check valve (36) and connect tester to the vacuum line.

2 Switch on ignition.

Note: The tester remains connected to the vacuum line medium green/yellow during the entire test.