Hi,
I've got a rather aged Vokera combi boiler (a 20-80 Flowmatic) which has recently developed a problem. Basically, whenever the hot water comes on in response to demand (and which works fine) the heating comes on as well, and after the demand has ceased the boiler stays on and the radiators heat up. The pressure dial goes crazy as well, flicking quite high accompanied by a loud clanking noise before settling down again.
It's almost impossible to stop it once started, as the control box is switched out completely (via the summer / winter switch), and the only way I have of definitely stopping it is by switching the boiler off at the main switch. Sometimes when I switch it back on the boiler fires up again!
It has the feel of a sticking relay or valve or something somewhere - is there anything obvious to check?
Thanks in advance,
James