[Andriy Dyachuk]

Pat,

On edit, I see Forest posted while I was writing my reply so I second checking the coolant level.  Here is my reply.

There was a recent thread on hot water cooling off that turned out to be low coolant level in the heater tank.

You can check the tank level by cooling off the heater (run the hot water for a while to get the heat out of the tank) and then gently removing the radiator cap.

If low, refill to the neck with 50% coolant and 50% distilled water.

Then check the tube from the radiator cap neck to the overflow tank.  If brittle and split, cut off an inch or so and re-clamp to the barb on the tank.  You must use a clamp to insure an air tight seal.

If your tank is full, the next suspect is the mixing valve located just below the black burner case.  To test with the heater up to temp (electric and diesel switches ON), turn on the hot water and feel the pipe coming from the tank to the mixing valve and feel the pipe going from the mixing valve to the coach.  Pipe from tank should get real hot and stay real hot.  Pipe from valve to coach should get real warm (120 degrees F) and stay that way.

With you experiencing hot water cooling off and a full tank of coolant, I would be looking for the pipe from the tank getting real hot and staying that real hot but the pipe from the mixing valve getting real warm and cooling off.  This is a symptom of a failed mixing valve.

The fix is to replace the guts of the mixing valve which is not hard to do.  Order the parts from Roger Berke at

http://www.parts.rvhydronicheaterrepair....egoryId=-1

The only fly in the ointment here is if you are using water from the water hose in cold conditions, the heater may not be able to raise the water temp enough for you to have hot water.  The spec is 55 degree rise in temp at a flow rate of 1.5 gallons per minute. So if your incoming water is 40 degrees, the best output water would be only 95 degrees and would feel cool.

The fix here is to turn the hose off and use water from the coaches fresh water tank.

Hope this helps you.

Trying to use the link for Parts what do you provide some reason it's not working do you have another working link for aqua hot parts thank you