The defroster works fine with the tint on the rear window. I use it alot in the winter no problem.

I keep the tint in the rear window lighter because with 7% stuff you can't see behind you very well when backing up, and you also can't see if there is a...cop or something back there that shouldn't be there. Don't think that you can't "see" things back there, its just darker and makes it more difficult to identify a cop and a crown vic with grandpa driving it. (shotgun in the window but its dark in the vic's and dark tint I can't see shotgun or interior light bar)