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

mazda
mazda3

#1

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.


#2

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).


#3

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.


#4

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.


#5

Is the carpet damp? Moisture will rush from warm to cold.


#6

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.


#7

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.


#8

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.


#9

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.


#10

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.


#11

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!


#12

You need to work at “drying” out the inside of the car. Water brought in on your boots and shoes can get soaked up into the floor mats and carpet. When you run the car turn the heater on “high” and run the blower on a mid-high to high speed. This will circulate the most air and the heat will help dry out the moisture. You might need to pull out the driver’s and passenger floor mats and bring them inside to dry out if they are really saturated with water.

I worked sales territories in snowy areas, upper NYS and upper Michigan, where getting in and out of the car 20 times a day tracked in a lot of snow, ice, salt, and muck into the car. When it was really bad I’d put an old towel down on the driver’s floor mat to suck up the extra moisture. At the end of the day the towel got removed and run through the wash. On occasion I did get ice on the inside of the windshield but the defroster took care of it quickly. The towel method was mostly an attempt to prevent the salt from killing my shoes and boots.


#13

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.

Yeah, living in Minnesota, I can certainly sympathize. I recommend you get some all-weather floor mats. They’re rubber/vinyl and so they won’t soak up the water from the snow and then sit there not drying out. They’re also a lot easier to clean than regular floor mats, and they don’t get stained by the mud and salt.


#14

Believe it or not, keeping a window cracked helps, too. Moisture (from the damp mats) can’t build up too much, due to the cold, and it ends up getting pulled out through the cracked windows. Give it a shot. While you’re driving - not while it’s parked.


#15

I’ve never had that problem, but never lived in an extremely cold climate either. I have lived in a place (Steamboat Springs, CO, USA) where I had to scrape off the outside of the window, but never the inside. I’m assuming you have fairly high humidity there too along with very cold nighttime temps.

Assuming you’ve verified there are no heater core leaks or door/window leaks or other sources of water entering the cabin, and that your ventilation system (heater, fan, vents, etc) is free flowing and working correctly.

Maybe switch to rubber floor mats? They don’t absorb moisture at least. In Steamboat sometimes the car wouldn’t start if if got too cold, so I had a gadget that heated up the engine installed. You plugged it in when you got home, and it kept it warm enough so it would start the next morning. I wonder if there’s something like that for the interior of the car available?


#16

The BEST solution is to spend your winters below Latitude 29…


#17

Better solution, garage.


#18

I have a 2003 Mercury Sable with horrible fog problems. It is only an issue in cold weather. The compressor is running when my defrost is on and I have tried all above suggestions (exp garage, out of my budget:). Is it possible that the flap or whatever that opens to allow outside air in (as opposed to recirc) is stuck? If so any suggestions on how to fix it?


#19

I Live Above The 45th Parallel. Iknow What Frost And Cold Are, Too.

Let me guess that you make short trips - 8,000 miles in one year - That’s about a fourth of what our cars go in a year.

The car is moist inside. Press your hand into the carpet in all four footwell locations and make sure it’s not outright wet, indicating a possible body leak.

Besides all the above comments, the car needs to be dried out. If you’ve got rubber mats covering the carpet, temporarily remove them and take a road trip or several road trips with the heat selector set to “floor” and fan on full blast. You may have to open a window slightly (or lots) and remove your jacket so that you don’t personally overheat.

Ideally, the car should have been parked with all doors open for awhile this past summer on a sunny day, but that ship has sailed.

You could see if there’s a kind person in a local body shop that would be willing to “bake” your car in a paint booth for you, but you’ll just need to plan on making some longer drives with floor heat at least once per week to maintain dryness.

CSA


#20

I’ve had similar problems (a light coat of frozen condensation that goes away when the defroster kicks in) with all my cars.
-Rain-X works but can also streak.
-A few minutes before shutting the car down (for instance, when I am about a mile away from home or work) I generally cut off the heat and open the window enough to draw the warm (and moisture-laden) air out, but close the window before leaving.