Boiler only fires up for approx 2 minutes (constant blue light) before returning to a flashing light, presumably until the water in the boiler cools down. Programmer is set to 20 degrees c but the room thermostat takes far too long to get to that temp, if at all. Under normal operation the boiler would fire constantly until the programmed setting is reached. Diverter valve works ok. I have read on this site that the problem could be faulty thermistors. Is that correct? I am not planning to carry out the repairs myself as I am not a qualified plumber. But some knowledge of the problem before I get a plumber in would be beneficial. Any help greatly appreciated.
