I wired all the components and did a bench test. With the polarity correct, the solenoid closes correctly. When you reverse the polarity, (as if the technician hooks up the cables backwards) nothing happens...it fails safe. At this time, I did not check the SCR in the over-voltage device. When the solenoid closes, power is also sent to the green indicator, next to the 5 amp fuse. If more then 16 volts is connected, the over-voltage SCR will trip the breaker.