Vacuum System

Data
Permissible looking per vacuum circuit 30 mbar/min at 400 mbar vacuum
(without vacuum reservoir)
Permissible leaking of check valve 60 mbar in 10 mm at 300 mbar vacuum
Permissible leaking of remaining components 20 mbar/min at 300 mbar vacuum







Special tools

Self-made tool
1 blind plug 000 987 11 45


NOTE: The vacuum test is subdivided into 5 test circuits (A to E). In the event of a given fault (e.g. legroom flaps not opening) the respective circuit can be tested first.

If a leak is suspected in entire vacuum system for heating, start with test step "a" and "b" and then test all the test circuits completely until the faulty vacuum circuit is found.

a) Testing check valve (31)







1 Pull vacuum line medium green/red and red/grey (on model 201.024 only) from check valve (31). Connect tester (arrow) to one of the two connections.
2 On model 201.024, close second connection on check valve with blind plug. Then evacuate with tester and read pressure gauge.
3 If the pressure gauge indicates an increase in pressure, renew check valve.

b) Testing vacuum reservoir (33) with vacuum line red/grey (model 201.024 only)







4 Pull vacuum line red/grey from check valve (31) and connect tester (arrow) to vacuum line.







Layout vacuum reservoir (33) under front fender left (model 201.024 only)

5 Evacuate with tester and read pressure gauge.
6 If readout on pressure gauge changes, remove reservoir (33) and check for leaks. Renew, if required or renew vacuum line red/grey.

Preparing for test







1 Pull vacuum line medium green/red from check valve (31) and connect tester to vacuum line.
2 Switch on ignition.

NOTE: The tester remains connected during entire test on vacuum line medium green/red.

A. Testing vacuum circuit 1, vacuum line medium green/red and input of valve unit 11 and 12

1 Push mode selection button "Defrost" on pushbutton switch unit.
2 Evacuate with tester (approx. 400 mbar) and read pressure gauge.







3 If readout on pressure gauge changes, test switchover valve unit (11) and (12) individually and test vacuum line medium green/red and renew, if required.







NOTE: If a leak shows up on vacuum unit medium green/red, the leak may also be on connecting hose (50) (maybe pulled off).

B. Testing vacuum circuit 2, vacuum element (40) for fresh air/recirculating air flap (short and long stroke) with vacuum lines

1 Push mode selection button "Vents Closed" on pushbutton switch unit and engage temperature wheel at "MAX".
2 Evacuate with tester (approx. 400 mbar) and read on pressure gauge.







3 If readout on pressure gauge changes, test vacuum element (40) directly or renew (83-165 section "D") or test vacuum lines medium green/light blue and medium green/yellow, and renew if required.







Vacuum circuit 2, mode selection () and temperature wheel engaged at "MAX".
40 Vacuum element for fresh air/recirculating air flap

C. Testing vacuum circuit 3, vacuum element (38) for defroster nozzle flaps (short and long stroke) with vacuum lines

1 Push mode selection button "Normal A/C and Vents" on pushbutton switch unit. Temperature wheel remains at "MAX".
2 Evacuate with tester (approx. 400 mbar) and read pressure gauge.







3 If readout on pressure gauge changes, test vacuum element (38) directly and renew, if required (section "B"), or test vacuum lines red/light blue and red/white and renew,if required.







Vacuum circuit 3, mode selection "Normal A/C and Vents" and temperature wheel engaged at "MAX"
38 Vacuum element for defroster nozzle flaps

D. Testing vacuum circuit 4, vacuum element (39) for legroom flaps with vacuum lines

1 Push mode selection button "Bi-Level" on pushbutton switch unit, temperature wheel remains engaged at "MAX".
2 Evacuated with tester (approx. 400 mbar) and read pressure gauge.







3 If readout on pressure gauge changes, test vacuum element (39) directly and renew, if required (section "C"), or test vacuum line medium green/white and renew, if required.







Vacuum circuit 4, mode selection "Bi-Level" and temperature wheel engaged at "MAX"
39 Vacuum element for legroom flaps

E. Testing vacuum circuit 5, vacuum element (37 and 41) for blend air flaps and heater valve with vacuum lines

1 Push mode selection button "Defogging" on pushbutton switch unit and set temperature wheel to "MIN" (not engaged).
2 Evacuate with tester, wait for approx. 5 seconds and evacuate again. Repeat approx. 5 times, because the vacuum element (37) is provided with vacuum by way of an orifice. Then read pressure gauge.







NOTE: If the temperature difference (preset temperature at temperature wheel in relation to outside temperature) is above 8 °C, the vacuum element (40) for fresh air/recirculating air flap is also provided with vacuum.







3 If readout on pressure gauge changes:
a. Test vacuum element (41) for heater valve directly and renew, if required Service and Repair or test vacuum line dark red and renew, if required.

NOTE: If the vacuum line dark red shows a leak, the leak may also be at connecting hose (50).












b. Test vacuum element (37) directly and renew, if required (section "A") or test vacuum line green and renew, if required.







Vacuum circuit 5, mode selection "Defogging" and temperature wheel at "MIN" (not engaged)
37 Vacuum element for blend air flaps
41 Vacuum element for heater valve
50 Connecting hose