1. Install a test gauge in the compressor discharge line.
2. Start the engine. Build up the air pressure.
3. Observe the reading on the test gauge when the compressor cuts-out. Compare the reading with the governor cut-out specification, 860 kPa (125 psi).
4. With the engine running, slowly reduce the air pressure in the system by applying and releasing the brakes.
5. Observe the reading on the test gauge when the compressor cuts in. Compare the reading with the governor cut-in specification, 725 kPa (105 psi).

If the cut-in or cut-out pressures are not within specifications, adjust the governor. Refer to Governor Adjustment Specification.

Perform the governor leak tests at the governor exhaust port for cut-in and cut-out positions.

For the cut-in position, check the exhaust port for inlet valve leakage by applying a soap solution at the port.

For the cut-out position, check the exhaust port, the mounting surface and the adjusting screw area.

If there is excessive leakage, replace the governor.