Volkswagen Golf/Jetta 2 manual

Air inlet pre-heater - testing
Fuel and exhaust systems - Mono Jetronic fuel injection / Air inlet pre-heater - testing


1 With the engine cold, detach and remove the upper section of the air cleaner followed by the filter element.

2 Check the air flap valve in the base of the lower section of the air cleaner for freedom of movement. Ensure that when closed, it shuts off the warm air passage.

3 Whilst running the engine at idle speed, check that the flap closes off the cold air passage.

4 To check that the temperature regulator is operating correctly, disconnect the two hoses from it (see illustration), connect them together and then note if the warm air passage remains closed off. If this is the case, the vacuum unit is defective. Where the flap valve closes off the cold air passage, the temperature regulator is at fault and in need of replacement.

4.4 Air intake components in air cleaner housing
4.4 Air intake components in air cleaner housing

1 Warm air nozzle
2 Cold air nozzle
3 Temperature regulator
4 Vacuum unit

5 The position of the flap valve when the engine is running is dependent on the temperature of the regulator. When the temperature is below 35°C, the temperature regulator should be open and the cold air


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