Re vaillant boiler?

You never know, it might.
White boiler, black front behind bottom cover and green knobs, combined temperature/pressure guage bottom right corner.

We can all be sarcastic, but YOU need the help!
As it says at the bottom of the question box:

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Now, drop the black cover down, look at the right hand side behind the pump, there is a brass diverter valve, on the side of that valve, there is a white arm that should move down when the tap is opened operating the microswitch below, if it isn't moving, the diverter diaphragm is shot and will need replacing.

If it moves down, but not enough to operate the microswitch it is worn but same result as above. As a temporary measure, you may be able to GENTLY bend the metal arm on top of the microswitch upwards enough that the arm makes contact and gives you hot water until the diaphragm is replaced.

Carefree
February 2011