I've been having some trouble with the with water on the door sill on the passenger side of my 147, with the recent heavy rain it's been filling up pretty quick so I got out today to try and stop it and save my carpet.
I was going to go to Alfa dealer and buy a new seal but I thought I would peel off the waterproof membrane and stick it down with some silicone just in case. I've had the door cards off before and checked the membrane for holes but it well stuck down so I never thought that it was the problem. Also the drain holes at the bottom of the door are clear and so are under the windscreen scuttle.
Took the door cards off and hid inside the car from the rain, and within a minute I noticed dripping not from the seals or the membrane but the plug for holding the door card on. (the one nearest the front)
I checked above the plug, bone dry and when I took the plug out water stopped coming in and as soon as I put it back it started dripping again.
Easy fix then?
Now I just need to wait and see, Might have guessed it stops raining now.
Iv'e seen a few posts about water on the sills but none really had a solution so I hope this helps somebody.