Yes the mixing valve on an Atwood XT 10 gallon water heater. Never seen one of these before. It states it equivalent to a 16 gallon hot water heater. It mixes the hot water with cold water via the mixing valve on the backside.
I have found some troubleshooting tips on the web.
For those who have not herd of one of these here's a link with decsription on an Atwood GE16-XT
http://www.americanrvcompany.com/Atwood-GE16-EXT-Gas-and-Electric-XT-10-Gallon-DSI-Water-Heater-94026-Camper-Trailer-RVNote the by-pass valve on the backside. This valve was in the normal setting (as shown) not by-pass.
I hear the mixing valve is about $100+ smackers. Will attempt to get mine back to 100%