Overboost Switch: Testing and Inspection

NOTE: While trouble shooting, always check the wiring, fuses and connectors for good condition and routing. Also check ground locations for good connection.






1. Connect VOLVO pressure tester/gauge #5230 or equivalent to hose at intake manifold.

Checking Switch In Engine Compartment:

Checking Switch Under Dash Above Brake Pedal:

2. Pressure switch is located next to coolant expansion tank or under dash above brake pedal.
3. Disconnect connector from sensor.
4. Connect a buzzer.
5. Increase pressure with pump. Switch should open (stop buzzing) at:

A pressure of: approx. 85 - 95 kPa (12.1 - 13.5 psi)

6. If switch does not open as specified, replace and retest with new turbo over-boost pressure switch.
7. Disconnect the test equipment and reconnect hose to intake manifold.