Hope this post will help someone down the line - today I took the "C" pillar trim panel off the passenger side of my daughter's '01 Alero. The defroster isn't working and I expected to find the melted modulator contacts some folks have previously posted reference to when a rear defroster is failing. Instead I found the contacts were in good shape. So I pried open the plastic housing that the modulator circuit board sits in and found the solder on one of the power connectors had melted off altogether. See attached photos. I re-flowed the solder to repair the board.
Note - the Alero I'm fixing is a four door sedan. It seems like you have to take the small section of the seat out (nearest the passenger rear door) to easily get the "C" pillar trim off. You don't - you can wrestle the trim free without removing the seat though it doesn't come off easily -it is only held in with clips. Eventually comes off. I couldn't get the seat portion out as the factory stripped the bolt-head holding the seat in.