General Question

Mat74UK's avatar

Why do the inside of my car windows keep misting over?

Asked by Mat74UK (4646 points ) December 17th, 2010

I understand that when the interior of the car is cold they will mist up but why when the car is warm. I use the air con constantly. The car is mainly used for short trips of about 5–20miles regularly.
It’s a 2004 Vauxhall Vectra Elite, anyone else had this problem?
The outside temp hasn’t been above freezing much for the past month.
What can I do to prevent this?

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23 Answers

lucillelucillelucille's avatar

You’re breathin’ in your car again,aren’t you??? ;)
Maybe you should have your coils cleaned.

ragingloli's avatar

When warm moist air hits a cold surface, such as a car window cooled by the sub zero outside, the gaseous water in the air will condensate on the window.
Not much you can do about it.

Adirondackwannabe's avatar

Switch from the air conditioner to the defroster. In cold climates the a/c does that around here when it gets cold.

Mat74UK's avatar

@ragingloli – There must be something as my van is fine and I breathe exactly the same in that!

meiosis's avatar

Have you spilt something in the Vectra? After I spilt a can of Stella in my Focus (don’t ask) not only did it smell like a brewery for a month it also misted up far more frequently. A spell of driving with the window open helped calm it down, but it still took ages for the problem to disappear.

Mat74UK's avatar

@meiosis – I know you said don’t ask but Stella in the car! You need something a little softer like Carling.
No I haven’t spilt anything let me just nag the wife
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Nope neither has she and how dare I try to put the blame on her!

Adirondackwannabe's avatar

@Mat74UK The reason the a/c mists and the defroster keeps it clear is when it gets cold and the temperature of the window is lower than the air inside the car the heat from the defroster is directed right at the window while the a/c vents are in the dash.

Anemone's avatar

It could be that your car is leaking some kind of fluid that’s ending up in your AC vent… or in the car cab. Extra moisture of any kind could be causing the extra condensation.

meiosis's avatar

@Mat74UK I was throwing a party last Christmas when I realised, already very well ‘refreshed’ that I’d left my phone in the car. Cue clumsy fumbling and unnoticed (until it was too late) spillage.

Mat74UK's avatar

@Adirondackwannabe – I can chose the direction of both the air con and heater and I have to blast it at full on the window or pull over and wipe.

Tropical_Willie's avatar

If you use the re-circulate it traps the moisture in the car.
Make sure the air is coming in from the outside.

Mat74UK's avatar

@Tropical_Willie – I’ve though of this and haven’t used the re-circulatory system since summer.

Tropical_Willie's avatar

@Mat74UK
There maybe a build-up in the vent tubes of moisture, or the drains are clogged with leaves and debris.

Adirondackwannabe's avatar

@Mat74UK I’m thinking the a/c doesn’t produce as much warmth as the defroster. I accidently hit the a/c buttton yesterday, in 15 degrees F and even on the warmest defrost setting the window had a little mist that never cleared. I’ll check that out tonight.

Mat74UK's avatar

@Adirondackwannabe – Ok let me know how it goes! I won’t be going out till tmw now.

robmandu's avatar

First question I have is to ask if your 2004 Vauxhall Vectra Elite even has air conditioning? It’s not as common in the UK as here since the summers there are milder.

The reason why the a/c system is engaged when you put it on Defrost is because that kicks on the dehumidifier, which removes moisture from the air. Your windshield then defogs because dry air is evaporating the moisture on the inside, not because the a/c is cooling the air to match the outside temperature. Indeed, most folks have hot air blowing out in Defrost mode.

If your vehicle doesn’t have a/c, or if the a/c is kaput, then you get the same drying effect once the car’s warmed up enough to blow hot air since the heat also dries it out. Also I’m thinking that, because you’re only going on short trips, it might be your car doesn’t get much chance to warm up enough to be effective.

I haven’t tried them personally, but you might consider evaluating some anti-fog windshield treatment.

Mat74UK's avatar

@robmandu – Yeah definitely got a/c. Believe it or not a/c is common here as it can get into the high 20’s low 30’s c in summer.
When I get the car warm I can chose the temp of the cabin and of late I have had it set at 28c or Hi blowing as fast as possible solely on the windscreen.
I shall go straight out and purchase some of what you recommend.

LuckyGuy's avatar

Are you losing antifreeze? You might have a small leak in the heater core. You would detect a slightly sweet smell.

Mat74UK's avatar

@worriedguy – you mean from the a/c sytem?
If so no I don’t think so. It is going in for a service in Jan i shall have that checked

LuckyGuy's avatar

No. Not the A/C.unit. The heater core has antifreeze going through it to warm you in the winter. It is usually located under the dash in the passenger compartment. Sometimes they get a small crack and leak a tiny bit. The warm air evaporates the antifreeze and it condenses on the windows. There are a couple of way to tell if you have the leak besides the smell. Notice how the condensate wipes off the window. If it smears it might be antifreeze. Also look for a wet spot on the floor up under your dash.
The Garage can find the leak by pressure testing your coolant system.

Mat74UK's avatar

@worriedguy – OK I recently checked the water level after the temp got to -17c I shall check again to see if it is losing any.

GabrielsLamb's avatar

Colder inside, hotter outside or vice versa.

Crashsequence2012's avatar

Has water accumulated in the car?

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