Borrowed a sportsman camper, hot water heater question

Turn the switch
on the WH to
on.

That way it
will work
on electric

You have a Suburban Brand Water Heater

The electric side and propane side controls are separate systems

Electric
120V AC with high/normal temp set of t-stats and OEM On/Off switch in outside compartment lower left corner. The inside switch and OEM switch are wired in series so BOTH have to be ON for electric to heat water.
Normal t-stat controls water temp to 130*F output (Hi t-stat trips at 170*F...manual reset)

Propane
12V DC with high/normal temp set of t-stats and On/Off switch inside with FAULT light. The inside switch turns propane on to heat water......Electronic spark electrode lights off main flame
Normal t-stat controls water temp to 130*F output (Hi t-stat trips at 170*F...manual reset)


MAKE SURE WATER HEATER TANK IS FILLED WITH WATER PRIOR TO USING EITHER
Electric element will burn out/short W/O being submerged in water within a few minutes
Propane can overheat tank and damage the porcelain lining inside tank

Make sure there is water in the tank before turning the heater on.

The two switches on the wall are probably Gas and Electric switches for your water heater. You can run on one, or the other, or both at the same time. You also need to check at the water heater if there is a rocker-arm switch. This switch needs to be "on" for the electric to work. If so, it's double swtiched for electric. Both the one at the water heater and the red switch inside need to be "on" for electric to work. If either is off, electric will not work, but gas will.

The switch on the water heater, behind the outside panel, is there for a safety reason. If there was only 1 switch (inside) and the water tank was empty, accidentally flipping that switch would turn on the electric. So only if there is water in the tank do you flip on the switch at the tank. Otherwise, it stays off, and the switch on the wall does nothing.

Before turning on the electric, make sure the water heater is filled with water. If it doesn't have water and you flip on electric, it takes only a few seconds for the electric element to burn out. (gas will still work though).

Even though you haven't told us anything about the water heater make / model it sounds from your description that it's likely a Suburban DSI with an electric heating element option. If so it could be run on both gas & 120 vac simultaneously for quicker recovery ... however, since this is a borrowed trailer I'd run it on gas alone and forget the electric option as there's always a danger of burning out the electric heating element if the water heater tank isn't filled properly with water.

The gas and electric portions of the water heater can be used separately or together. Merely turn the switch to the on position.