TAmes

Hi all,

I have a 2010 550i. I've noticed that warm/hot air seems to always come out of the vents near the windshield, regardless of how I adjust the temperature setting using the knob or using iDrive. If I shut off the windshield vents, then the airflow does stop, but I'm wondering how to turn down the temperature so that cool outside air comes out of the windshield vents. Would appreciate any thoughts.

Thanks,

TA

uheenada

I don't think you can. I have 2005 545i and mine doesn't. I really hated this cuz here in Phoenix, the weather gets hot and i want to cool down my valentine 1 radar detector while driving by blow cold air through windshield vent but it always blow hot air.
So I always need to take off the detector and hold it in front of center vent

vkhong

Windshield air is warm by design. Prevents condensation from forming on glass.

subarashi

Only blows warm air..in auto mode, the windshield vents seal off unless you have the heating on at which point warm air will flow out.....

uheenada

Umm I belive it doesn't matter the temperature of the air as long the ac is on.
My other ride doesn't. It Blows nice cold air and gets rid of the condensation.
It's a desgn flaw IMO.

sessionmc

Are you sure? Most defrosters use warm air.. cold air may work because the air temperature is still high than the condensated glass, but that's guaranteed to take much longer than a nice flow of warm air. It like melting ice with cold water... it will still melt but not efficiently at all.

uheenada

Yes sir, my previous vehicles are 2000 acura integra, 2002 Honda accord, 2003 Infiniti G35, and 2004 Lexus RX330 all had cold cold AC air blowing
During the summer, it was always cold air and during the winter, it were all hot air unlike E60 which always blows hot air.

Pioneer530

I agree that it is a design flaw. Never had a car that did this. I just turn the windshield vent off during the summer, it's easier than dealing with heat in 90 degree weather.

TAmes

Guys, thanks for the replies. I find it baffling that BMW designed the airflow from the windshield vents to always be hot, but I'm comforted that there isn't something wrong with my car. I'll just have to switch off the airflow from the windshield vents -- even in 70-degree weather, it gets a little warm inside the cabin with these vents running.

sessionmc

Avoiding Frost and Fog on Windows - http://www.dctech.com/physics/features/0103.php

"#4: warm the windows Your windows will be colder than the air inside the car. This is especially true if cold rain or snow is hitting them, but with a constant flow of cold air against them as you drive they will naturally cool down. You need to direct the warm air from the vents against the windows to compensate for this. The bigger the difference between the air and the window temperatures, the lower the relative humidity that will still fog the windows up. This can be illustrated with the doubling every 10oC rule. For example, suppose the air is 20oC (68oF), and a window is at 10oC (50oF). If the air in the car is over 50% relative humidity the window will fog up. If the window is at 0oC (32oF) it will fog up if the air is above 25% relative humidity. Hence, warming the window by even a few degrees can make all the difference between a window fogging up or not under given conditions.

#5: keep outside air flowing over the windows #4 emphasized using warm air flow against the windows. Even if the air isn't warm, the fact is that outside air - having been colder - will probably be drier than the air inside the car. The drier the air against the window the faster the water can evaporate off because there is less condensing back on from the air. You can demonstrate this by putting a little water in two saucers. Leave one standing, set a fan blowing over the other. The one with the fan will dry out faster (both will take a long time, depending on how much you put in). The one without the fan gets moist air over the water surface from evaporation, and without that being pushed away it is soon condensing back in about as fast as it evaporates.

Something curious I've found is that fogging windows isn't exclusively a winter phenomena. We sometimes get the windows fog up on hot humid days and long trips. With the air conditioner running full time in the car the windows can become enough cold compared to the outside air to start fogging up on the outside. This only happens significantly near air vents, so an obvious solution is to change the vent direction. If it happens on the front windshield there are always the wipers to help out. Failing all else... it might be necessary to turn off the air conditioning for a while. "

What you consider a BMW design flaw is actually an improvement others haven't caught on to today.