I have a vokera compact 28 boiler. When I turn the hot water tap on the boiler fan starts then stops then starts, this stopping and starting of the fan continues for about 2 min, then when fan is finally established the boiler ignites. Sometimes the boiler stays ignited and sometime the boiler stops, and then the fan starting and stopping resumes. Central heating is ok. Sometimes when the boiler ignites the water from the tap is only warm. I've been told it might be a thermister thats faulty but the problem seems to be the fan not being able to establish to allow the burner to ignite.
