if its just a humming sound,and the fan is definately not running,then I would say the fan is siezed.
ken knight, December 2009
Did you ever get to the bottom of this problem as I am experiencing the same thing.
Anne, June 2009
Potterton 40e should be automatic ignition (lighting when required)
My boiler was also making a humming noise (potterton profile 80E) and my fan was faulty..
You can check if your fan is working by seeing if there is air flowing out of the flue or by opening the case and checking if the fan is turning..
Sometimes cleaning the fan bits seems to work (by taking fan apart, cleaning it and putting parts back again) although a new fan will cost you about £100.
If your fan is working then the air pressure switch may be faulty or your pressure tubes may be blocked..
