I noticed recently my demisting was poor so I took the dash apart and of course found the tube up to demister had come out of the sleeve. I replaced as you do.
However one of the things i'd noticed was that with the regular blower on to demist I was getting a draught against my leg - seemingly coming from around the fuse box cover. That didnt go away even when i replaced the heater hose. When I dropped the aircon box I found that where the speaker on my passenger side (I am LHD) is now screwed into the aircon panel instead of the conventional dash, that has left a large hole in the old dash, out of which all my demisting air was beeing blown - down into the aircon cover, and onwards to the floor. I just made up a plastic blanking plate for the hole and its now like having a diferent heater unit.
Now I'm not sure if someone in the past had removed a piece that was supposed to be there (we bought her second hand), or whether this is just a dreadful design floor :doh:, but if you have aircon and suffer from poor demisting then just a few minutes spent blanking that hole could really remove a lot of frustration.
