Temperature problem with Truma Water Heater

dorsettaffy

I have a 2007 Ace Jubilee Envoy and the Truma water heater has started giving problems.  When switched on to electricity - very rarely used on gas - it heats up as normal, but after several hours stops heating and produces only luke warm water. If I switch
off at the control panel and then switch on again after a few minutes it again works normally and heats the water very quickly. Switching off and on again quickly does not work - it needs at least a couple of minutes. This is particularly annoying first thing
in the morning when we want hot water for washing etc. There have not been any problems with fuses blowing or the unit tripping out, just the loss of heat. Any ideas please?

Dorsettaffy