mld

Hi I wonder if anyone can help me? I have just returned home after along spell working away and tried turning my Baxi Solo 3 PFL40 on, it powers up, fan starts, piezo sparks, pilot light ignites and stays on, so all lights on so far but when the burner (final light) starts to come on the solenoid starts to chatter like mad, the final light is trying to come on but just can’t make it. It seems to be tied in with the chattering, after about 20 to 30 seconds it shuts down. Any ideas ??? Thanks.