How can I fix my Potterton Promax Combi HE 33 Plus A Range Boiler?

Hi

We have a Potterton Promax Combi HE 33 Plus A Range condensing combination boiler fitted along with a Myson MPRT programmable room thermostat.

The boiler/heating is continuing to run even with the thermostat/heating switched to off. However, the hall radiator is the only one which is hot, all the others are thermostatically controlled and are stone cold.

I have switched the boiler to hot water only and the boiler has now shut down on the heating side as per normal operation. Any ideas what the problem might be?

Dave
January 2011