First major complaint I have. Rear passenger windows won't defrost

[mobilekid]

So, today is one of the first cold and snowy days here in Calgary. What I noticed is that no matter how much I blasted the hot air the back two passenger windows would not clear up at all. Other than wiping them down, any other tips to get these windows to defrost?
I did for the most part have the hot air on the windshield. I did attempt for about 5 minutes to blow air from the front vents but then my front windshield started to fog up again and I reverted back to putting air on the front windshield. It was roughly a 30 minute drive so I would assume plenty of time for the whole car to hear up. I had the car set to circulate the air inside the car. Would setting it to take air from outside help clear those two windows?

[dani3d]

Yes you need ot have it from the outside air, and you must use the defog setting which tune on the AC as well. that really help.

[AlphaMicra]

The two outer round vents on the dash should blast the same air that comes out to your windshield when you have it on full front window defrost (ie; turn left knob all the way to the right, turn fan all the way to 4). If you're only getting the windshield and not the two side vents when you do this, something is wrong. Take it back to the dealer to get this fixed.

[MetroMPG]

Yes, use the fresh air setting. Otherwise, you're recirculating humidity.

Let us know how it goes next time.

[Daox]

Ditto on the fresh air option. A/C helps, but usually isn't necessary.

[Howie]

rainx on the inside windows sometime helps...

[KKaWing]

rainx on the inside windows sometime helps...

Don't do it, when windows fog up, it'll frost, like real ice frost. Don't ask how I know... Better to just roll the window down and hope the weather stripping wipes some of it off.

[Evilbred]

Don't dump air directly on windows, this will tend to have air deposit humidity directly on them, prolonging the time to defrost.

If you have AC, it will help a lot to remove humidity from the cabin air. If not, then only time will help. Colder air and longer defrost times will be better than hot air, as hot air carries more humidity.

[AlphaMicra]

Technically speaking, hot air has a greater capacity to retain moisture per unit of air compared to the same unit of cold air; that's why we get dew and frost in the shoulder seasons as the air cools overnight. The drop in temperature has a similar effect as would wringing out a saturated sponge. However, the simple act of heating cold air doesn't introduce more humidity to that air. If the HVAC controls are set on drawing fresh air from the front cowl on a dry cold day, the air blowing on the windows will be just as dry as the originating cold air coming in. If there's any precipitation, that would introduce a source of humidity that would get into the warm air, and that's when I'm glad to have the AC come on to help clear the windows.