We have had a water heater in our Sportsmobile Sprinter for 9 years. Used it maybe once. We don’t use hook ups since we mostly camp off grid and I can’t remember to turn the hot water on when we are driving. Been thinking about pulling it out and using the space for something else.
There’s no way to test it so it’s a gamble. Looks like a very old style with no electronics so the chances of it working are pretty good. I have a newer style with an electronics board that crapped out. I ended up buying an entire new water heater for not too much more than just a new electronics board.