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How to stop frost on windshield on the inside of the car?

I have a 2008 Mazda 3 with 63,000 km / 39 146 miles.
I bought it last year used with 50,000 km / 31 068 miles.

It is my first car and I have no car servicing experience.

I park my car on the street.
Last winter I noticed that I frequently got frost on the windshield on the inside of the car. Is there a way to stop this from happening?

This winter I want to avoid having to scrap the windshield on the inside with the heater on max.

Do you know if installing a window deflector will help?
I am thinking that if I leave one of the windows slightly open but covered with a window deflector that frost will not form on the inside of the windshield. Is this correct or just wishful thinking?

Thanks.
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Comments


  • Does the car have AC?? If so turn the AC on (if it doesn't automatically turn on when the defrost is on...like some cars do).
  • edited October 2011
    Frost on the inside is VERY strange. You likely have a leak somewhere. Either the windows, doors, or sunroof are letting water into the cabin, or there may be a coolant leak in your heater core.

    Do you smell anything inside your car? Sweet smell means coolant, musty smell means mold from an outside leak.

    Typically there is not enough moisture inside the cabin to form frost on the inside--I have lived in cold climates all my life (PA, NY, MD) and have never seen frost inside any of my vehicles.

    Leaving a window cracked may help but you should fix the leak if you in fact have one.
  • In my experience, most cases of interior window icing are the result of one or more of the following car owner mistakes:

    Using the recirculate function on the HVAC system
    Failure to remove as much snow as possible from shoes before entering the car
    Failure to remove wet floormats from the car in order to dry them
    Keeping windows open, rather than using the HVAC system (on the A/C setting if necessary)

    If none of these situations is applicable to you, then you may want to explore the possibility that the heater core is leaking. While this is not a strong probability on a car that is just a few years old, it is possible.
  • Is the carpet damp? Moisture will rush from warm to cold.
  • edited October 2011
    Interior window frosting means there is moisture in the cabin of the vehicle. Unless the outside air is very dry, leaving the windows open or cracked will probably make matters worse. Look for wet carpets caused by a clogged evaporator drain or another source of water intrusion, such as drain channels for doors, trunk lid, or sunroof, if so equipped. If the cowl or evaporator box is loaded with leaves or other debris, this can also cause an overwhelming amount of water to flow through the evaporator box during rain, causing the carpet to get wet. Dragging too much snow or water into the car from outside can also leave the carpets wet and cause interior window frosting. Try running your air conditioning to keep your cabin dry, even if it's cold out. Leave the a/c on, but use the heat control to stay comfortable. You will still be warm, but the air will be dry, which will probably help a lot. You could also try supplementing that by cleaning the inside of the windows (dirty glass is more prone to collecting moisture, and they're probably dirtier than you think, especially if you smoke) and using a fog preventing product on the interior glass. Rain-X makes a product for this purpose, but I don't know how well it works since I've never used it. It may be worth a try, though.
  • Frost on the inside is pretty normal where I live. The leak is you. You breathe, expelling moisture, and then you park the warm moist car in the below-zero weather and the moisture freezes on the windows. Mark also called it with the snow being deposited in the car from your boots. The Rain-X works pretty well until it gets into the -30 or so range, at which point nothing works but to start the car 10 minutes before you leave to let the defrost warm the windows.
  • My brother learned a trick when he had a '68 VW bug--these are known to have anemic defrosters, to put it mildly. Leave the windows partway open on a cold night (when no rain or snow is forecasted) and the moisture will be drawn out of the car. I have used this method on occasion when my cars have had frost on the inside (due to my tracking snow into the car) and it works.
  • I agree with shadowfax. I have had the same problem on several cars that I have owned that had to be parked outside. One car was my 1965 Rambler Classic 550 that didn't have carpet--just rubber floormats. You could use my dog's technique. He rides with his head out the window, but this method isn't very comfortable in freezing weather. Other than trying Rain-x or keeping a window cracked open, you probably just have to live with the situation.
  • edited October 2011
    good ol' school chalk sticks are absorbent much like the silica gel packs inside of packages you buy.
    Place one in many hidden locations like door pockets, glove box, under each seat etc.
    -- heck, if you can save some of those silica gel packs, use those too.

    Take measures to not introduce moisture yourself like drying out the mats and kicking off as much mud or snow as you can.

    When the oportunity presents itself,
    have some windows open a tad and run the heater on high to push air out of the cabin while drying some.

    do not park the vehicle with the a/c-heater in the recirculating mode.

    My 06 Escape hybrid had interior frost two seasons in a row till I did these things.

  • Thanks for the responses everyone.

    **
    Do you smell anything inside your car? Sweet smell means coolant, musty smell means mold from an outside leak.
    **
    I have not smelled anything out of the ordinary.

    **
    Failure to remove as much snow as possible from shoes before entering the car
    Failure to remove wet floor mats from the car in order to dry them
    Keeping windows open, rather than using the HVAC system (on the A/C setting if necessary)
    **
    I think the floor mats are adding to the moisture in the car. I don’t remove the floor mats. It gets really cold up here in Canada that when I am done driving, I just want to rush indoors.


    **
    Try running your air conditioning to keep your cabin dry, even if it's cold out. Leave the a/c on, but use the heat control to stay comfortable. You will still be warm, but the air will be dry, which will probably help a lot.
    **
    I will do this.

    Thanks everyone!
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