Extractor fan (bathroom ceiling) broken?

[Big-D]

Hello. 2 questions:
1. Took cover off fan to remove soft obstruction from fan blades .. bits of loose wadding of some sort ( - a bit like old asbestos?? - tho this is a new house just 2yrd old). Should there be a grille or something in the flue to stop wee birds & beasties & traffic noise from getting in? ( - I can see daylight at end of shaft, which has a cap mostly covering it).
2. Tried to adjust fan overrun using 'dial screw' on PCB (turned it fully both ways) then it refused to work when I put it back together again. Have checked all wiring - seems sound. When I turn on light I can see the fan blades turn over *very* slowly, but the motor isn't properly kicking in (I can hear a faint humming noise from motor). I've tried turning dial to several positions - but no joy. Any suggestions what's happened/how to cure? Is it duff?

 

[jj4091]

probably.

 

[Taylortwocities]

That isnt asbestos, its years and years of soggy human cells being sucked into the fan.

There should be a non return flap at the end (or in) the pipe to stop the winter gales blowing into your bathroom

 

[Big-D]

Thanks TTC. The material is mostly fibrous and has hard bits in it (plaster?) - I'm wondering if its perhaps building debris (roof insulation?) that's recently worked loose?
No sign of a grille or mesh in flue - only a 'mushroom cap' over the end of pipe. What should I use ideally?