worcester combi 30cdi

[angelpie]

hello can anyone help, this boiler is about 3 years old and the problem started after i switched the electic off to fix a light fitting, when the heating is on and its getting up to the temp on the room stat and say i use the hot water it is knocking the heating off, i know water comes 1st, but even after tap is turned off the heating does not come back on. and the icon on the boiler flashes that it as lost its signal. i have changed the batterys in the room stat. can anyone help me please...