My Ariston Microgenus 27 MFFI is now six years old and has been serviced every year. Over the last few weeks we have noticed that the boiler does not shut down when desired temperature is reached. Room stat is working fine, but boiler just carries on heating the house until turned off. Whilst it is doing this, none of the temperature lights on the front of the boiler are lit.
Could it be a faulty gas valve? Any suggestions welcome.

Chris Heaton, March 2009

it's very odd that there's no temp indication lights on when this is happening. if the boiler was being asked to fire up by any source it should still show this! sounds like it could be a faulty PCB. best get an engineer to call

andy gas man, March 2009