The default position for the relay is "send power to the solenoid". Solenoid opens, fluid flow is enabled, OD should work. This assumes the solenoid works, nothing else is blocking the fluid flow, and the OD valves and parts themselves aren't shot.
Hitting the button toggles and latches the relay in the "off" position, sending power to the light instead. Solenoid closes, fluid flow is cut off, OD disengages.
Hitting the button un-latches the relay, which returns to the default position... light off, solenoid open.
When you turn the car off, the relay automatically returns to the default position.
