What brand do you have. On our Thetford there was a loose hinge clip that slowed the valve to open before letting water in. Kind of hard to repair in place but can be done.
It is not a relay because it does not have any control wires. It looks like a like a diode to keep auxiliary power from feeding back to the battery. The arrow stamped in module is the key. Since you have a Freightliner chassie you need to contact Fr...
