Go to an RV parts store for a winterizing bypass kit for the water heater. Use POTABLE RV antifreeze and follow the instructions on the bottle. Drain all the water out of the water tank. Install the bypass kit on the water heater if it doesn't already have one. Put the water heater in the bypass mode. Add the antifreeze to the water tank. Open every water faucet including the shower head one at a time until antifreeze is present. Do this for hot and cold on every faucet. Once that is done, turn off the water pump and open all the faucets. That's all there is to it. Rember... DO NOT use automotive antifreeze. It will kill you.
Don't mess with it just bring it to the dealer that you bought it from