Pictures, pictures.
Somewhere, probably at your control/switch panel inside the coach, there should be a red light switch, as seen in the lower left of Photo 1. When operating on 120V, it will light up red. To run on 120V, the switch on the face of the water heater (if it's a Suburban) must be in the ON position (Photo 2). Some will have a pin holding the switch off. Remove it and turn it on. BE SURE THERE IS WATER IN THE TANK! To operate on 12V/propane, the small red rocker switch on right side of the monitor panel (Photo 3) needs to be turned on. Initially, the small red LED next to it will glow, but will go out when the propane fires up. If it doesn't go out, there is a problem with the water heater controls or there is still air in the gas line. Turn off and retry after a minute or two.
Yes, you can operate the water heater on 120V and propane at the same time for faster recovery. We normally just use the 120V on a seasonal site and run the propane system occasionally just to be sure it's working.
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