When there is hot water demand a diaphragm pushes a pin that rocks and arm that pushes another pin to operate a 3 port valve, the arm also operates a microswitch. Sometimes the microswitch breaks. More often the diaphram gets a hole in it. You need to download the manual from the Vokera website. Diaphragm replacement is easy, turn off the cold water inlet, remove the fulcrum arm (one slot head pivot screw) and then unscrew the five hexagonal/philips headed screws that cover it. It is very very important that you remove all traces of the old diaphram from the plastic pusher plate and from the brass insides, or you will be fitting another before the year is out.
Its a standard part in the boiler maintenance kit.
Better still, get a Corgi man who is familiar with the model to fit a maintenance kit t0019, make sure he also cleans the flue venturi, if he doesnt know what a flue venturi is, or doesnt know why it needs cleaning on this model, find a gasman who does.
c++, December 2010
