I have the same problem.had low water presher first changed the govener restrictor.worked fine but the heating side of the water goes on and off.the boiler is closest to the kicthen sink so it shuts off quicker when using it in the kicthen,takes longer to shut off when using the bath.tried adjusting the pressure still the same.if turn on the water full takes longer to cut off.but on slow run it cuts off quicker.
Any sugestions please
H, April 2009
