[FrankJ]

First double solenoid valves stay in the position last energized. So your piston can be either in or out. There is a manual actuation button on each end of the valve next to the plug. You can play (excuse me test) with that to make sure your plumbing is correct. You should only have one light on at a time otherwise you will get confusing results.

There are spring centered valves, but you most likely do not have one.