Air Control Governor, cross to Bendix P/N 275491 or Midland P/N 18530;

Application and General Information 1:Standard Version. Pressure setting range is adjustable. Governor - Signals the unloading mechanism on the compressor when to build up air to the reservoir and when to halt air build up. Usually between 100 and 120 psi. This item controls the pressure in the air system. The compressor runs continuously while the engine is running, so the D-2 governor activates the compressor's unloader mechanism when system pressure reaches the governor's cut-out pressure. It deactivates the unloaders once system pressure has dropped to the governor's cut-in pressure. While unloaded, the compressor simply pumps air from one cylinder to the other rather than send it to the tank.