MiraExcel B Cartridge

Regarding the temperaturefluctuation or cool running it could be a faulty cartridge however to checkthis, see if you can get hold of the hot supply pipe before it enters theshower or perhaps as it leaves the boiler.

If when holding this pipe thetemperature fluctuates or goes cool then the problem is not with the shower butmore likely with the boiler as the shower can only deliver what the boilersends to it.

Disregard the temperature at thetaps as they have a different flow rate.

If the above is Ok then it's best just to replace thecartridge, however it is probably worth stripping the cartridge out andchecking that the inlet filters are clean, before buying a new cartridge.

To replace the cartridge

Turn off hot and cold water supply

Pull front temperature knob off The rest of the knob assy.just unclips

Remove 4 screws that hold cartridge into body

Pull old cartridge forward shouldn't be too tight

Set new cartridge for High/Low pressure (instructionswith cartridge)

Slip new cartridge into place remember to check that the newseals are all in place (and don't drop out as you push back)

Tighten screws be careful not to over tighten

Refit knobs.

Turn on water and test. (Occasionally you will have to resetthe cartridge temperature, instructions with cartridge)

Easy peasy!!!!

Cartridge   Mira903.33  This cartridge supersedes theprevious high and low pressure versions

Link to cartridge

http://www.showerdoc.com/shower-spares/mira/MIRA-903-33-Cartridge-Assembly-(Up-To-2003---Black)-Comes-with-seals