When I try and adjust the temperature it goes from cold to hot with no mixing at all. As you increase the mix by turning the knob to higher numbers, you hear the thermostat kick in and the water temperature changes from cold to very hot.When you turn the knob back to regulate the temperature, you hear it kick out again and it goes cold.

Peter C, November 2009

Hi, the T80si is an electric shower so it doesn't mix water. When you turn the knob to the higher numbers the water flow is reduced and the water temperature goes up (power stays the same). There is no thermostat, just thermal cut-outs (like thermostats but for safety). More investigation is needed, if the water is going completely cold then it is likely that the main cut-out is operating, if the water is going from hot to luke warm then it is likely the outlet pipe cut-out is operating. These should only operate when the water is too hot to touch (above 50 degrees C). You could get these parts checked out first. Good luck.

Paul M, November 2009