NOTE: The illustrations shown will be of the SS model single cylinder air compressor. Differences in procedures for Holset® models SS, QE, ST, and Cummins® air compressors will be illustrated where necessary.

Remove the air governor or air governor line from the air compressor unloader body.

Operate the engine to activate the air compressor.

If the air compressor is pumping, the air governor is malfunctioning and must be repaired or replaced. Refer to the OEM service manual.

NOTE: Not all air compressors referenced can be used on your engine or application.

If the air compressor does not pump, remove, clean, and inspect the air compressor unloader valve assembly. Refer to Air Compressor Unloader Valve. Refer to the Holset® Air Compressor Master Repair Manual, Bulletin 3666121.

If the unloader valve assembly is okay, clean and inspect the exhaust valve assembly. Refer to the Holset® Air Compressor Master Repair Manual, Bulletin 3666121.