I've just replaced the TCO switch, which was definately faulty (overheat light, cold water, switch open circuit) and my shower now operates again, however, the water temperature is only just about adequate when the temperature dial is full on the red, while on the high setting. The flow is therefore low, but no warning light has come on. Before the TCO fault, having the temperature dial just over half way was sufficiant, and here the flow was good.
Has anybody got any ideas on what my problem is ?
Thank you.

Karl, October 2009

thanks guys. Ive checked the heater elements, and these are fine (not open circuit) and all connections are tight. What is my temperature pressure valve ? This sounds like the TCO I have already replaced. The fault diagnosis in the mira manual points to the PCB ? What confuses me, is that it was fine before the TCO failed. I do have another working shower of same make/model, so I could try swapping parts over ?

karl, October 2009

Sounds like the unit is simply not delivering enough heat. On high power the second element is switched on; if this is burned out (open-circuit) the high power light will be on, but the heater won't work, leaving you with only medium-power heat and flow. If you are competent to do so, check the continuity of the heaters at the tank electrodes after FULLY ISOLATING the unit. Or work your way through the fault finding chart on page 23 of the manual, which is on the Mira site at http://www.mirashowers.co.uk/onlinecatalog/pdf/mira_sport_max_1.pdf. Otherwise, it could be a loose connection or a burnt-out relay, but a loose connection would overheat very quickly and make itself known, and relays tend to fail closed (contacts burn and weld) so not so likely as an open-circuit element.

PlumbSpark, October 2009

HI There
It sounds like your temperature presser valve needs replacing if the shower is less than twelve months old it may be still under warranty
I am retired Joiner plumber/election/builder.(LT West Yorkshire)

trampus09, October 2009