I have an ideal classic boiler and recently has failed to fire up, I have knocked the side of the boiler and it will fire up for upto 10 minutes and then shuts off again. I have taken the cover off the boiler and found a small plastic propeler, I believe this has come from the top of the fan, can anyone advise if this is why the boiler is not firing up properly and does this mean that the fan needs replacing. Thanks