Mike. I have just this week had the same problem. The answer to mine was that the temp control and the temp limiter has failed. They are situated underneath the electrical elements. To get to them you need to take the gas fire out. This is simple but involves getting under the van in order to disconnect the gas pipe that feeds the heater. The fire is screwed to the caravan floor, four screws and its out. The two parts are inside a metal plate, one screw holds it in place. I got my replacements from leisure supplies who posted them to me at a cost of £14.05 for the two. Part numbers 65100 and 65200. My fault was very similar to yours and had been going on for some time.
Ronnie Walker, March 2012
