Checking the APC System In the Car

Checking the APC system in the car

Tools: Pressure gauge 83 93 514
Hose with connector (included with the pressure gauge)
Air pump (radiator tester)

1. Remove the pressure transducer hose from the inlet manifold connection.

Seal the inlet manifold connection.




2. Connect the pressure gauge to the hose from the pressure transducer (as from 1983 models, the hose from the pressure switch). Position the pressure gauge vertically to avoid erroneous readings.




3. Connect the air pump via the hose and connector to the hose from the pressure transducer.




4. Start the engine and increase the speed to at least 2,100 r/min (in order to make sure that the APC system is in operation).

5. Increase the pressure to 0.50 bar (6.6 PSI)

6. Check that the solenoid valve starts to operate (chattering sound).

The fact that the solenoid valve starts to operate is an indication that the components in the APC system -knock detector, pressure switch, control unit and solenoid - are working.

If the solenoid valve does not start to operate, see the Fault-tracing chart.