This question is regarding Mira Excel/Select Thermostatic Cartridge - 903.33

Pressure control impossible to turn

Is there something preventing the setting of the pressure control that needs to be released before attempting to turn the control? It doesn't turn however hard I try. What is the function of the black knob with an (apparent) screwdriver slot in the centre of the control? Is this something to do with the problem?
Asked 7 years ago by John
These cartridges are sometimes hard to set , but a spray of WD 40 may help.

I have never needed to touch the black knob to adjust anything so would tend to leave it alone.

Answered 7 years ago by Barrie Seabright

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