I have an 89 300SE and have been noticing my rear window getting a bit "milky" around one edge and sure enough, the defroster isn't working in that area.

It looks kinda cheap when your driving such a nice car the the rear window has this three inch line of frost going across it...and of course right across the area I need to see!

Is this an expensive replacement?

Mattman: I replaced the rear defrost switch in my 82 300SD and it worked great. I bought the part from:
www.************************

They specifically cater to Mercedes and they've got things you've never seen before. Super customer service too! (No, I don't work for them:p )