Checking function

• Start engine and run at idling speed.
• Switch ignition off.
• Observe position of lever on intake manifold flap change-over valve (2nd technician required).

• The intake manifold flap must (after ignition is switched off) close and after approx. 3 seconds open again.

If change-over does not occur, perform the following checks:

Fig 1: V.A.G 1390 Connected To Vacuum Unit

Courtesy of VOLKSWAGEN UNITED STATES, INC.

• Pull vacuum hose off vacuum unit - 1  -.
• Connect hand vacuum pump V.A.G 1390 or equivalent to vacuum unit.
• Operate hand vacuum pump and check intake manifold flap change-over mechanism for ease of movement and operation.
• Check vacuum lines for correct connection.

If no malfunction is found in the mechanical components:

• Check intake manifold flap change-over valve.