SEAL 1P4880 - Caterpillar

Sudden movement of the machine or release of air under pressure can cause injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the air system and brakes.
Before you disconnect any line from the air compressor, purge the system of pressurized air.Failure to purge the pressurized air before you service the air compressor can result in personal injury.
Start the engine and allow the air pressure to reach the minimum cut-in pressure of 689.5 kPa (100 psi).
Allow the air compressor to fully cycle. Check that the air supply has built up to the system specifications. Use a soap solution in order to check for air leakage in the fittings and the air lines. Repair any fittings or lines that are leaking.
Operate the air compressor through the loaded state. Operate the air compressor through the unloaded state. Verify that the governor activates at the proper cut in pressure and cut out pressure for the governor.
If necessary, adjust the air compressor governor:
Remove cover (1) on the top of the governor.
Loosen the locknut on the adjustment screw.
Turn the adjustment screw counterclockwise in order to raise the cutout pressure. One turn of the adjustment screw changes the pressure approximately 165 kPa (24 psi). The cut-in pressure will change the same amount.
If the adjustment screw does not change the cutout pressure, the unloading valve in the air compressor is not working correctly.
The air compressor must quickly cycle between the loaded position and the unloaded position. This may be checked by installing a test gauge in the unused unloader port of the air compressor. Observe the gauge during the change from the loaded position to the unloaded position. The air pressure should be applied quickly and the air pressure should be exhausted quickly. There should not be any lag between the buildup of the air pressure and the release of the air pressure. If prompt action is not noted check the installation for a restriction in the lines.