Hi all
Any help very gratefully receved.
My Baxi 105e has been fairly trouble free for 5 years or so.
Lately however, it has started to carry on on the preheat setting (burner on, flashing green water neon) when the heating is turned off, after reaching the thermostat temperature, for 30 minutes +.
This results in hot water "leaking" into the radiators so that  in effect the heating is still on when it's off according to the stat.
I've "cured" it by turning off the preheat setting.
My insurance emergency plumber has changed all the microswitches and put an external pressure regulator vessel in, but it still seems to do as above, so I've turned the preheat off.
Any clues anyone?
Thanks
Bob