I have 2007 monaco knight 38pdq. And the relay is behind the water heater. There is also 120v plug into outlet located there. Access is inside bay besides the water heater. Open door, pull out drawer and squeeze into bay. 12v from the switch outside bathroom on panel operates gas and with the switch next to it operates with 12v thru 120v relay. All this 12v go thru the water heater control box first before the 12v relay.