There are many reasons why a water heater won't work on electricity, but we have some simple suggetions to try before you call a repairman.
1. Go to the outside of your coach and take the door off your water heater, look at the small electrical connections on the relay switch, pull them off to see if there is corrosion, loose connection or damage. Sometimes they just need to be scraped or the connectors just need to be squeezed together for a tighter fit, or the need some die electric grease or vaseline. Also look for damaged wires.
2. On a water heater that has both propane and electric, there are 2 thermostats, The electric thermostat can go bad and need to be replaced. They are fairly easy to replace and not to expensive, around $15-$20.
3. The water heater also has a heating element that might be bad. This is a little more tricky to remove the element , as it is a little tight getting a proper wrench around the the element to get it out, but again not very expensive at $15- $20.