Why Will My Potterton Boiler not control the radiatiors properly?

There's a motorised valve that decides where the heated water should go - Radiators or Hot Water Tank - or both at the same time - Diverter Valve. Sometimes they get stuck in the wrong position and strange things happen.

Here's a picture of one... it has a manual override lever...

http://www.toolstation.com/images/library/stock/webbig/60151.jpg

You may need a specialist to attend to your valve... Avoid British Gas if you want to hang on to your money.

Good luck...

Peccavi
November 2009