Just replaced the diaphragm in the diverter valve, and lubricated the spindle with silicone grease. Although the spindle does now rise when DHW is called, the tap needs to be opened quite a lot, and even then it still doesn't quite rise enough to operate the micro switch to fire the boiler.

Any suggestions?

is maybe the inside of the valve sticking and maybe the whole thing needs replacing?
Or, I did wonder if maybe I installed the diaphragm upside down (just a thought)? I installed the part with the spring to the top.

Martin Clewlow, May 2008

firstly, did you check and clean the inline filter on the rising mains into the boiler? this can get very clogged and restrict the flow throught the boiler, hence the flow switch being lazy)

Also, when you replaced the diaphram, did you clean out the little feeding orifices on either side as they get crudded up and reduces the flow pushing the diaphram.

T, May 2008