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 electric unloader models are normally three steps of unloading. These can be identified by three electric solenoids mounted on the capacity control cover. 100% unloading is also available and these models have four solenoids. 100% models are fully unloaded on startup only. The first step of capacity control loads as soon as oil pressure is established. There are three main components in this system, the unloader regulator assembly, the solenoids and the unloader yoke or power assemblies.
The regulator assembly controls the oil supply from the oil pump to the yokes by opening or closing the supply oil lines to the yokes. The regulator has an internal piston for each step of capacity control, either three or four. Each piston is controlled by an electric solenoid. When energized the piston moves to open supply oil pressure to the unloader yoke. When de-energized, oil is bleed off the piston and the return spring closes the oil ports.