I have Pro Combi CT29 boiler which refuses to work. The pump runs the fan does not kick in (althou it does turn freely. I do have power to the fan but have not measure what voltage nor checked the Neutral. The three lights display flashes a few times and you can hear it "hunting" then it goes to red and nothing happens. I am told by a Gase Safe Engineer that it is the fan but he appears uncertain.

These are not cheap nor returnable - so is there anyone who knows with greater certainty?

Martin Williams, November 2015

At a distance greater certainty is impossible...

Were I in your situation I would disconnect the fan and run external power to it and check it that way.

It is always possible that the fan is good and that the neutral return path is open circuit but it would be a very strange fault.

My money - based on what you say - is resting on a defective fan motor but that too would be a very strange fault.

Your Gas Safe engineer makes a reasonable guess - which is unusual.

Good Luck..., November 2015