[TomCat]

This seems to be a rather common problem. I had the same thing on my 2017 MHC 305RL. We bought it used in 2018. When I turned on the electric water heater element I smelled burning wires. We just didn't use it. Finally got around to looking into it a few weeks ago and traced it to the junction box (plastic) where the supply 120v connected to the water heater. I could see the plastic on the junction box (not really a box - just a covering) melted. I had to twist my body and arms between drain pipes, furnace ducts, etc. to just be able to reach it. Turned out that the 120v wires were connected with wire nuts, and the hot side was the culprit. I stripped back the burned part of the wires and reconnected using crimp on connectors. That fixed it - my water heater now works on 120v. It was probably a poor connection right from the factory, but I agree that I would be very hesitant to use wire nuts in any connection because of all the vibration over time.