The governor is out of adjustment.

Adjust the governor.

The governor is leaking.

Check the governor for leaks. Overhaul or replace the governor. Refer to Air Compressor Governor Valve Replacement Air Compressor Governor Valve Replacement.

The air compressor is leaking.

Check the fittings, the bolts, and the mating surfaces. Tighten or repair as needed.

The unloader is not functioning.

Overhaul the cylinder head assembly.

The governor is faulty.

Overhaul or replace the governor. Refer to Air Compressor Governor Valve Replacement Air Compressor Governor Valve Replacement.