I have a ravenheat white star combination boiler,it suddenly decided not to turn off,its on all the time,I have had to turn off every radiator which is ok in summer, but soon I'll need the radiators on,and so they will stay on all the time unless I go into the garage and switch the boiler off.I have had two heating engineers who are trying all ways to fix it but as yet no luck,new diverted valve,tried new pcb,thermistors, help!

Des Webster, September 2016

Try removing the programmer or disconnecting the input to the boiler

toptrish, September 2016

Oned would have thought the engineers would have tried to narrow doen where the fault is but, just on case, suggest this:

Disconnect the room thermostat at the boiler to eliminate that and its wiring. If the boiler goes off, there is a fault in the termostat and / or its wiring. If the boiler doesn't go off, there is a fault in the boiler.

Reading this thread suggets it may be worth thinking about a new boiler (And not a Ravenheat one):

http://www.fixed4free.com/answers.php?id=65201

XXX, September 2016