Like j-d, my hot water heater did not work on 120v. I replaced the 120v heating element, but unlike j-d the new element solved my problem. When operating on 120v, there is no flame. It works like a over-sized coffee maker. A heating element that looks like this heats up the water.
BTW: If you do an ohm check across the element terminals and determine it's bad and remove it, BE PREPARED for a rush of water by placing lots of bath towels around it. Even though you drain the tank, about 1/2 gallon of water remains inside to submerge the heating element to protect it just in-case the tank is empty but the switch is accidentally left on when the RV is plugged into 120v. According to the tank manufacture, freezing does no harm.
