Mira Sport Max - Warm/Cold - Overheat light

[WuTan]

Help please if you can Smile

I have the Mira Sport Max - I have searched this forum etc but cannot find an exactly similar problem or one with a definitive answer and solution...

Had the shower for 2 years. Over this time I have had to increase the temperature dial from half way to 3/4 of the way to achieve the desired temperature. Recently the unit will cut out - i.e. the overheat light will come on and hence water temperature will go cold (allowing the system to cool back down). Then the overheat light will go off and the water temp will increase again for say a minute or so, and so on. The cut out (overheat) seems to occur at quite low temperatures (water still feels tepid) - i.e. I would not have thought that it should only cut out if the water coming out of the shower was quite hot.

Flow seems to be good (pressure does drop off at the higher temperatures but I think it is acceptable). I have checked various items with the multimeter (although far from an expert) i.e. Heating rods seem to have the right resistance. Continuity across the Thermal Cut Out Switch (TCO) until it trips and the overheat light comes on.

Any ideas would be appreciated - Could it be due to limescale in the heating tank? Could it be a faulty TCO that cuts out to early? etc etc

Cheers in advance.

 

[gas4you]

Are you in a hard water area?

If so it sounds as if the heater element has scaled up.

 

[WuTan]

Its definitely not a soft water area.

Thats what I am suspecting due to the fact that over time I have had to increase the temp dial to get the same temp. But I am not sure that this should suddenly cause the Overheat condition to trip all the time. Could this be the case? What does the TCO connect to and monitor? Is it just the water temperature or is it element temperature?

I would just like to be as sure as possible before I replace the heating tank (reasonably expensive part).

Cheers