taking forever to defrost windshield

I bought an '89 525i. It is a beautiful car and I love it. However it didn' t come with an owners manual and so I have been trying to figure out how to get the defroster to work. I can get it to blow air through the vents on top of the dash, but it still seems to take forever to get the windshield defrosted and then it is difficult to keep up, unless I stop breathing or something. Any help would be appreciated. The blowers are working fine, perhaps part of it is it seems to take awhile to get warm (I live in Chicagho and it was 0 degrees this morning so maybe this is to be expected???).

Thanks for any help.

Paul Blosser

Hi, Paul-
I'm assuming you have the same three-knob setup as my BMW has. The top one plugs/opens the vents for the defroster. Move the top knob to the left, those vents are closed. Move it to the right and they are open.

The middle one lets cool air flow from the vents at about knee-height from the console. Left is closed, right is open.

The bottom knob controls air blowing out of the heater vents on the floorboard. Left is closed, right is open, although there's something extra: when the knob is to the left, no outside air is coming in, it'll only blow hot air if you have the fan on. Move that knob to the right and hot air will flow whenever you're moving, even if you don't have the fan on.

The best way to set those knobs to get your defroster to rock and roll is to move the top knob to the right and the bottom two knobs to the left and turn the fan all the way up. If you look closely to the left of the knobs, you'll see a little diagram which is supposed to make this clear to you, although it might as well be hieroglyphics, since no one seems to figure it out without the manual.

Also, there is a separate fan for the air conditioning. It's the button with the bright blue light that comes on whenever you push it. If that button is pushed and that light is on, the only air flow you'll get will be from the middle vents. It over-rides everything else. Which is too bad, really, because I like being able to have the air conditioning flowing through the defroster with the heater on. The AC removes moisture from the air, and that dry, warm air will zap the frost on the inside of the windshield in seconds. My Honda will do this, but that's verboten on the BMW...
Make sure your AC button is not pressed!

Good luck!
4DF

Thanks for the help. I figured the bottom of the three buttons is for recirculate and I can only use this periodically. When it is pushed in the air in the car is much warmer, but also mush moister and my windshield fogs up. I drove for an hour on Monday and kept the ionsdie of the windshield clear by alternately turning the recirc off and on and periodically craking my window open a little to get some of the moisture out.

Today (wednesday) everything seemed to be working much better, of course the outside temp was about 32 degrees warmer. Are the heaters in these cars just not that great. I had a 69 Opel GT that you would have thought the Germans didn't know anything about heaters!

I think I might also check into rebuilding the heater control valve on the firewall. That may help.

Thanks again.