Capacity Control on the Chrysler 2000 and 3000 series compressors is accomplished by mechanically lifting the suction valve disks off the suction seats. When the valve is lifted all refrigerant in the cylinder is pumped back into the suction side of the compressor on the piston up stroke. There are two types of unloading on these compressors, suction controlled or electric unloading.
The suction pressure unloader controls are the same on all models. There are three main components in this system, the unloader body and piston assembly, the unloader bellows and spring assembly, and the unloader yoke or power assemblies.
The bellows and spring assembly control the position of the unloader body piston. This is done with a mechanical linkage between the two assemblies. Three forces control the position of the bellows rod, suction pressure in one direction and the range adjustment spring plus external air pressure or atmospheric pressure in the other direction. A balance to maintain a desired suction pressure is achieved by changing the spring pressure using the external adjusting nut. The knurled nut and lock nut are used to prevent a step from unloading if this is needed.
The unloader body and piston assembly controls the oil supply from the oil pump to the yokes by opening or closing the supply oil lines to the yokes. Two detent balls and springs in the unloader body give each step a positive action. All the compressors with suction unloading have three steps.