[RussWhite]

I'll take a shot at the explanation David and Teresa.

The solenoid is an electrically operated valve - a very small one. When the compressor is running, the valve received voltage and is energized causing it to close. This is called a normally open valve ( solenoid ). So when the compressor is running, it does not let air or water out of the bottom of the water separator. But when the compressor stops, the valve becomes de-energized and it opens. Then any water and the air between the compressor at the check valve at the inlet to the auxiliary tank is released. This accomplishes two necessary functions. One it unloads the compressor so starting it next time is easier, and two, it drain any water in the separator. I had to modify my valve a little to get it to work properly. When de-energized is was not really opening all the way. Hope this helps. Russ