To achieve 100% full capacity, the vents that were open to reduce capacity are closed. This is achieved by a DC solenoid inside the compressor. A 24-volt AC signal sent to the rectifier and converted to a 24-volt DC signal to operate the DC solenoid inside the compressor moves the bypass ports that allow the vents to be covered and uncovered. The loading and unloading of the two step scroll is done without shutting off the compressor between first and second stage operations. During startup of the compressor, even if full load is needed, it will always start unloaded, and after five seconds it will switch to the 100% full capacity.

While the unit is operating, your suction pressure will change as it switches from low to high capacity. The compressor current will also increase as it switches from low to high stage. When there is no 24-volt DC signal, the solenoid coil is de-energized, and the compressor is in low stage. When the compressor is operating in high stage, there is a 24-volt DC signal that energies the DC solenoid.

To test the operations of the loading and unloading of the compressor, there are certain procedures you can do. First, measure the compressor amperage while the unit is running. Cycle the unloader on and off from low stage to high stage, and then back to low stage in thirty second intervals. You should see at least a twenty percent increase or decrease in compressor amperage.