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Checking intake manifold changeover valve N156 > < Special tools and workshop equipment required

A3 Mk1

Test sequence
Test sequence
–  Run engine at idling speed for 2 or 3 minutes. (During this time a vacuum is built up. It is required to switch the intake manifold).
  Note!
The vacuum reservoir is integrated in the intake manifold and cannot be replaced separately.
–  Switch off ignition.
–  Unplug connector from intake manifold changeover valve -N156-.
   
–  Connect one of the contacts on the solenoid valve to engine earth using test leads and crocodile clamp from -V.A.G 1594 A-.
–  Connect the other contact on the solenoid valve -N156- to positive using remote control -V.A.G 1348/3A-, adapter lead-V.A.G 1348/3-2- and auxiliary cable.
–  Operate remote control -V.A.G 1348/3A- for approx. 2 to 3 minutes; throughout this period the vacuum unit should remain energised.
If vacuum unit does not remain energised, check unit as follows:
–  Detach vacuum pipes from vacuum unit for intake-manifold changeover.
–  Connect hand-held vacuum pump -V.A.G 1390- to vacuum unit.
–  Operate hand pump and observe changeover.
–  Check vacuum unit for leaks. (The vacuum unit should not return to rest position until the hand pump is vented to atmosphere.)
–  If necessary, replace vacuum unit.
–  If vacuum unit is not energised, check -N156- for blockage as follows:
  A24-0075
–  Connect one of the contacts on the solenoid valve -N156- to engine earth using test leads and crocodile clamp from -V.A.G 1594 A-.
–  Connect the other contact on the solenoid valve -N156- to positive using remote control -V.A.G 1348/3A-, adapter lead-V.A.G 1348/3-2- and auxiliary cable.
–  Operate remote control -V.A.G 1348/3A-.
–  Check valve for obstructions (remove vacuum hoses and blow through).
–  If necessary, replace intake manifold changeover valve.
–  If none of the preceding tests has revealed any faults, check vacuum system for leaks.
  A24-0075

Checking intake manifold changeover valve N156 > < Special tools and workshop equipment required