Our Suburban electric element just went out on our 3 month old 5th wheel. NuWa is sending us a new one and they will then deal with Suburban with the warranty issues. DH says it will be an easy repair. Ours still works. The water reaches the max, about 180 degrees, then the limitor shuts it off. Water gets dangerously hot.
Here's another possibility, don't know if you have a new unit, we have a new 2012 Mobile Suites and after 2 months, same thing, no hot water on AC, propane worked fine. A mobile repairman said it was the thermostat, Drv sent a new one, a 5 min repair. When he took off the old one, he said Suburban had installed a propane thermostat on the AC side. I have no technical knowledge so I have to take his word for it. However, he called me back a few days later and his Suburban water heater on his brand new Carriage did the same thing. Also, some friends in AZ called to say their water heater did the same thing, they also have a new Mobile Suite. Seems to me someone on the assembly line ran out of AC thermostats and just put in what was handy. There should be a recall.