Old Biscuit is correct, it is a GEH16EXT model and, looking at some schematics, it has a mixing valve which is probably the problem. Unfortunately the back side of the heater is very difficult to get to. It may be necessary to remove the heater to get to the valve. I am going to let some experts spend their time and my money this next week. Thanks to responders.
Thanks to those who have replied. Should have stated that the outside shower and bypass valves have been checked. Also, the coach has never been winterized. We follow the birds south. If there is a check valve on the downstream side of the tank I am going to let a professional work on it as the tank is difficult to access.
I have an Atwood 10 gal gas/elec water heater that no longer provides hot water. The water in the tank is hot but it is not getting into the hot water line. Initially, I was using the elec side and the water turned cold so I switched to the gas side thinking that the elec element had gone bad. I got hot water but not as hot as it should be. Not even that has gone away. I flushed the tank and the water that came out was too hot to touch. Have I got a one way valve that is inop or is there an air block? Little tough to evaluate since the tank is not easily observable. This is on a 2008 Itasca Horizon.