hey all. i have a 1983 300sd. it's getting kinda cold here, especially in the morning, so i have been trying to turn on my heat. i turn the dial all the way to max (in the red) and it just blows cold air? the air conditioning works great- i used it this past summer. i can't tell if the air conditioning is coming on when i try to turn the heat on or if it is just blowing the outside cold air or what, but it is definitely blowing- it's just not warm. i let the car warm up plenty before trying it- so i know that can't be it. i replaced the heater hose (the hose that goes from the block to the heater core) very recently- so that is all good. any ideas? also, my rear window defroster isn't working either. the switch works and lights up, but nothing seems to happen. is there a fuse i can check? anything else? thanks for the help guys.

red