Boiler control

[Mafopp5]

After years of no problems, my boiler now operates only on its internal thermostat, even when the timer is off. I thought it might be the frost stat, but this checks out okay. To shut it down at night I have to turn it off at the mains. The fan seems to be permanently on. It is a Potterton Neataheat. I am about to change the RWB9 programmer, but any other ideas out there?

 

[gas4you]

Check the live supply from the programmer. If it never goes off then it will confirm the programmer at fault.

 

[bengasman]

fan permanently on? could be low speed to facilitate pilot. could be faulty diverter

 

[chrishutt]

Motorised valve micro switch stuck on?

 

[Mafopp5]

Thanks for all the responses. I think it may be the programmer and will change that next week. I'll also check the motorised valves in case their microswitches have stuck. great help thanks.