Frost inside windows and sunroof

ktklobe · Post by **ktklobe** » 09 Feb 2019, 08:35

I’ve looked around the forums without luck, if I’ve missed this topic can someone forward it. 06 S40 T5 and I keep getting frost inside of the main windshield and a ton on the inside of the sunroof. The posts I’ve seen mention snow and antifreeze remain in the carpet. No snow here, just bitter cold temps. No coolant issues. We’ve been from 6 to 17 below freezing and I notice it every day. I’d also noticed condensation in late summer and fall after rains. I’ve cleaned out the sunroof drains, one was plugged....but I still don’t understand what the F is the point to let water past a closed sunroof to drain.... once the drain was cleared, moisture condensation stopped. Drains are open and I can’t figure out why I get frost, and not a little bit on the inside...I don’t recirculate the cabin air either....any help is greatly appreciated!

Post by **RickHaleParker** » 09 Feb 2019, 15:57

Humidity from your breath, snow on your shoes or from the air gets trapped when you shut off the car and close the door. Condenses and freezes as the temperature drops. Try leaving a window or the Sunroof cracked and see if it makes a difference. The idea is that water vapor can escape before it turns into frost.

ktklobe · Post by **ktklobe** » 09 Feb 2019, 16:27

I’ll give that a try, and it has rained here a lot the past several months. None of our other vehicles have this problem, which is why I’m perplexed? We’ve had, maybe an inch of snow total this winter and none before this started. I drive two miles to work and very little other then this. The sunroof is what caused me concern the other morning, I literally need a scraper to get through the frost on the inside of it....

Post by **RickHaleParker** » 09 Feb 2019, 18:54

Two miles to work and little other. In other words the cab never gets warn enough, long enough to dry out.

Post by **RickHaleParker** » 09 Feb 2019, 21:14

I think I got it worked out.

It is normal for the water in the air to condense when it is cold. This includes the air inside of the climate control unit.

I think what is happening in your case is: The heater vaporizes the condensation in the climate control unit. This raises the Humidity in the cab. Because of your short drive, the high humidity air never get pumped out of the cab. You park, turn off the car and trap the high humidity air in the cab. As the temperature falls, the humidity condenses, then freezes as frost on your windshield and sunroof.

You might stick a Hygrometer in the cab and see if you can get correlating data.

Another thing you could try is run the fan on full all the time. to get a rapid exchange of air between outside and inside.

For your driving pattern you most definitely need a blower in tip top condition. If you plan on keeping the car for years, it might be a good idea to stock up on OEM Blower Motors before they become NLA (No Longer Available).

ktklobe · Post by **ktklobe** » 13 Feb 2019, 06:43

Windows cracked just a fraction when it’s not raining and keeping the blower on high is seeming to help. I’ve has one steamy encounter the last few days, but it’s been raining for the past 3 to 4 days. I think a few more days, and a little extra drive time will hopefully finish drying everything out. Thanks again

difflock54 · Post by **difflock54** » 15 Feb 2019, 01:52

Try a small dehumidifier fora couple of days.

cpace2013 · Post by **cpace2013** » 12 Dec 2019, 06:26

Hi,

I have the same issue with my 2006 S40 Volvo. I tried leaving two windows cracked but it only seemed to make the problem worse. My next step is to spray Rain-X on the inside of the car overnight. I am nervous to drive my car especially in the afternoon/night when light is low and the car fogs up. The air doesn't blow quick enough for me to see the road. Any other suggestions?

Post by **RickHaleParker** » 12 Dec 2019, 17:13

cpace2013 wrote: ↑12 Dec 2019, 06:26 the car fogs up.

This is critical: Are you getting frost, fog or a sticky residue on the windshield?

cpace2013 · Post by **cpace2013** » 13 Dec 2019, 11:30

The windshield will fog up. In the mornings there will be frost inside the windshield.