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Discussion Starter · #1 ·
So after work today I got in my car and noticed there was condensation on the inside of the windshield right above where the air blows on the windshield. The car had been parked in the parking lot for almost 10 hours so I'm not sure where this came from? Anyone else experienced this or have any insight as to what this might be from??
 

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What was the temp outside? If there is a large difference between outside and inside temp you can get that on glass. I wouldn't worry.
That's what I thought. It did cool off this afternoon but it was the weirdest thing because it was in the exact shape of the vent on the dash and only in that spot inside the windshield.
 

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Short version:
If you ran your front defogger/defroster on the way to work then that could be the whole issue, which means there's nothing to worry about.

Long version:
The reason is because when the system is in defog/defrost mode it uses the AC to dry the air, making it clear a foggy windshield more quickly. That's because it can heat dry air more quickly since it has less moisture in it (doesn't have to "boil" water) and it has a greater capacity to absorb the moisture that's on the windshield. Once you turn off the engine, though, the moisture that was condensing on the coils inside the airbox, which was drying the air, is now being warmed by the refrigerant (R-134a) as the pressures equalize. The way the AC system works is by compressing the R-134a gas into a liquid, pushing it to the front heat exchanger, then to the airbox coils where its design causes it to lose pressure and boil off, becoming a gas again, and collecting heat in the process. This is where it feels cold to you in the summer. So, when the pressures equalize, the simple effect is where it was removing heat and feeling cold, it now gives off heat and feels hot. This causes the condensation previously collected to now get warm and become a fairly dense vapor which rises and collects on surfaces, especially ones that are noticeably colder by comparison. This is the same as when a glass of iced tea sweats on warm summer days.

Sorry that was so long but it should give you a fairly decent insight into why it's happening. A good practice to observe when you start using your AC in warm weather is to switch it to non-AC (vent or floor) for the last several minutes (keeping the fan blowing) to allow the cold coils to warm up with air flowing over them, moving the dense, moisture-laden air away from the coils and drying the remaining moisture that has already collected. When you don't follow this practice, over time the moisture that sits in your airbox that has no air flowing mixes with dust, etc., and starts to smell funny. Sometimes it even smells so bad that you have to have it cleaned professionally, but that's fairly rare, I'm sure. If you've ever gotten in your car on a warm or hot day after using the AC, parking it for a while, then coming back to it and smelling something kinda foul, this is the reason. The simple fix is to follow this practice, and best of all it's free!
 

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So there I was driving tonight, it was a hour and a half trip and I was about half way through it. The defroster was set at 70 degrees and out of no where the windows fog over. Tried to clear them by changing the temp to cooler and then warmer, both with no luck. Finally got to the point where I didn't feel comfortable driving because I couldn't see and had to pull off to the side of the road. Now to say the windows were fogged up would be an understatement, the windows were litterally covered with heavy moisture. So much that the windows had to be wiped and dried and still wanted to fog up. I read the posts about similar problems and even noticed a weird smell just prior to the windows fogging. The rest of the trip the entire heating and cooling system seemed sluggish. I am going to call the dealership first thing Monday morning. Any one have any ideas on what the problem could be?
 

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It sounds like the heater core is leaking! The smell you're talking about and all of the windows being covered is the give-away. Coolant, which is HOT liquid, leaking into the air ducting will instantly fog every cold window it encounters, and leave an oily residue, especially on the windshield since it is in the direct path of the air exiting.

What car do you have? What year? If you put that info into your signature or avatar then that'll help us. This could easily be covered under warranty if you're still within the period. Do you have an extended warranty? They have different levels of coverage so check into that as well.

Let us know how it turns out.

If you have no coverage or just need to finish your trip, get some Bars Leaks powder. It works! Warm up the engine with the cap off, pour it in, drive. After not very long it'll find and seal the leak. I had a Ford 302 heater core burst in the middle of a 5-hour February drive heading home. Dude at the highway gas station did this and it worked for over a year! (This was twenty years ago, too!)
 

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I have an '05 Malibu with the same problem. When it gets cold out I have to stop my car to scrape thick frost from the inside of the windows.

I took it to the dealer and they could find no leaks in the heater core; the tell-tale smell of coolant was notably absent. They've checked the system drain for blockage but that wasn't the problem, either.

They've dried out the car but they told me to wait until it gets warmer--great, so I made two trips to the dealer and missed work for them to tell me to wait until winter's over.

Does anyone have any other suggestions?
 

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Does your heater even work? If you're scraping frost from the inside during the winter, then you don't have enough heat to keep it from freezing up. Moisture might be a problem down the road, but frost on the inside means one of three things: 1. there's not enough hot "water" getting to the heater core to give off enough heat, or 2. the defroster door just isn't diverting the air to the windshield, or 3. the air pathway is blocked.

Starship and a couple other techs can tell you if your heater doors are driven by vacuum or electricity, but stick your hand up there and see if any air is even coming out.

Also, if your AC isn't working anymore it could be like a car I had in the past. The freon was leaking at the heat exchanger inside the car. The oil in it was slowly coating the heat exhanger fins and collecting dust. Over time it choked off the air so much that there just wasn't enough coming through. A cleaning of the coils and a repair of the freon leak fixed it for good.
 

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The HVAC actuators are electric. In fact, generations 6 is so much closer to 7 than 5. Anyway, there has to be too much moisture inside to be just condensation. Is the carpet wet on one side vs. the other? I wonder what they found that needed to be "dried out."
 

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The bottom half of my windshield gets a nice thick coat of frost occasionally. When I scrape it off, its enough to make a small snowball the size of a ping pong ball. Never have I had something like this happen on any of my previous cars.

GM has lots of issues with water/moisture coming into the cabin. The Buick Enclave is notorious for it too.
 

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In winter we tend to track a lot of snow into the car with our feet. With the heat on the moisture enters the air raising the humidity inside the car and when we shut down and leave the car, the glass cools first and the water condenses on the glass and freezes. What I do is try to leave the car in the sun with the windows down an inch when I can. Even on a cold day it warms up enough inside the car to get some of the moisture out.
 

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In winter we tend to track a lot of snow into the car with our feet. With the heat on the moisture enters the air raising the humidity inside the car and when we shut down and leave the car, the glass cools first and the water condenses on the glass and freezes. What I do is try to leave the car in the sun with the windows down an inch when I can. Even on a cold day it warms up enough inside the car to get some of the moisture out.
I appreciate the advice but i don't agree with it. . I put an electric heater in the car for 4 hours and cracked the windows . and 3-4 days later the same thing. I realize that sometimes you see other cars with ice on the inside of the window but that doesn't mean it is normal . I have been driving for 35 years and never had this happen so often.

Whats worse is the dealer is telling me that if they can't duplicate the problem they can't diagnose it. My feeling is that even if it leave it outside for a week and it finally ices up its not going to tell them why . All they will have is a window that iced up for some reason.
 

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Bullheadpond, I have a 2012 Malibu, and I can tell you that icing on the inside of the windshield is not normal. I drag snow into my car every day just like everybody else, and have no icing. It doesn't matter if my vents are on recirculate or outside air. Still no icing. My afterblower is not turned on either. All I can say is that if you are getting icing on the inside of the windshield, it is being caused by a high humidity level inside of the car. If you want to fix it, you need to find the source of the high humidity. It might be something unusual like rain or melt water draining into your heater box. If engine coolant in the cabin were causing the problem, you would smell it and note a loss of coolant, so I believe you already ruled that out.

Here is one possibility. I believe when you turn on defrost, the AC also starts running. The purpose of this is to condense out water from the air before it is warmed and sent out to the cabin. You might want to check to see if your AC is running while on defrost and if not, have it fixed. You did mention that you have a fogging problem in the summer. This problem may somehow be related to the AC system and/or heater box.
 

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@Clothseats

I've had frost inside the car on rare occasion too, and it is almost positively the result of tracking water/snow into the car. The sun heats up and evaporates moisture in the cabin, and rapid cooling after sunset in the winter leads to condensation.

In life, the most simple explanation is usually the correct one. Simply leave the windows open a crack on a sunny day like Drunken Elvis suggested. I find it unlikely the HVAC system would create more moisture in the cabin (especially while the car is off) than tracking in snow and rain water.
 

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Nerd, I understand the thinking about dragging moisture into the cabin every time you enter the car in the winter time, and I agree that this does happen. I believe, though, that a well-functioning climate system will keep inside moisture low enough to avoid frost on the inside of the windows. Maybe it is because the climate system dries out the interior while driving so that when the vehicle is idle overnight, the humidity is so low inside the cabin that the humidity level can't rise to the point where it will cause frost. Anyway, I have never had interior frost, and we have seen some nights of -30 degrees F this winter. We all seem to agree that the frost is caused by excess humidity inside the cabin (not rocket science, but a sound starting point). Therefore the way to solve this issue is to pinpoint the source of the excess humidity. With some careful thought, I am sure that possible sources can be isolated and proven out one way or the other. Maybe proceeding in this way will show that the cause is from tracking snow/water into the car. My personal experience doesn't show that so I could be wrong.
 

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I've never seen that much frost on the inside of a vehicle. I'm guessing the A/C condenser drain may be clogged or there may be a leak somewhere allowing water into the car.
 

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During cold weather the A/C compressor does not run for any length of time. Normally air enters the car through the cowl below the windshield and exits the car by way of an outflow valve in the rear of the car. I don't know where it is in the Malibu. In the trunk? Perhaps it is blocked or stuck shut. This would prevent warm humid air from exiting the vehicle when the heat is on.
 

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@DE,
Yes the valve is in the trunk. I've seen one on the driver's side and there might be another on the passenger's side.

@All,
If the climate control system (CCS) is capable of drying out the interior enough to prevent moisture from forming on the inside of the windshield that would later freeze, how is the air inside the cabin kept dry when you open the door to exit the vehicle? Even if you don't track in water/snow, the door is open long enough to completely nullify what the CCS was able to do to the air inside.

I agree with ClothSeats in that you need to find the source of the water. If you have a sunroof make sure the drains are taking the water all the way to the ground. The AC runs in the winter but not long. However, if the AC drain is plugged then the passenger's carpet will be wet up front and maybe even in the back. If it's soaked then no amount of AC will dry it this time of year. It will need to be removed and dried externally or replaced.

See if the door seals are in good shape and keeping water from getting by them to the inside.
 
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