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    macmaster05 Senor Member

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    I noticed this the past few days during the rainstorms and cold days. After parking my car for hours, I notice that the windows fog up inside on their own (when I return from work for example). I seldom use the AC and heater, but if I do I always turn it off, but I do leave my vents open. I've never had any of my cars do this, at least not that I can remember.

    Is something going on with the vents? Sound normal to you? Maybe I like this car so much that I worry too much and notice every little thing about it...?

    And yes, the car is completely powered off.

    Thanks.
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    hyo silver Awaaaaay

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    Given the unusual weather you're having, the interior humidity is no surprise. We typically use the 'air conditioning' more in winter than summer, just to clear the windows.
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    firepa63 Former Prius Owner

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    Leave your system in Auto AC and your problems will go away.
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    Paradox Prius Enthusiast / Moderator

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    When the windows fog run the ac compressor, it'll clear them up. Leave it on though, once off in a while they'll just fog up again. Sounds normal...
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    paprius4030 My first Prius

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    I got yelled at before for this suggestion, but it's true. Windows that have a film on them fog up easier, so make sure the windows are super clean in addition to running in the auto a/c or defrost mode.
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    Paradox Prius Enthusiast / Moderator

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    Rain-X also sells a No Fog application for the inside of the windows. It works but I am not a fan of it. Rain X is a phenominal product, but the no fog stuff makes the inside look weird at night under lights. I haven't used it in over 10+ years though, so if the formula has changed it may have improved.

    On a side note about the rain x anti-fog, I do have a very and I mean very old bottle which I use on the mirror in the bathroom to keep it from fogging after showers and for that application it works quite nicely.
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    macmaster05 Senor Member

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    Thanks for all the suggestions so far. Most all of you advise turning the Auto AC on while the car runs, which of course I do when they're fogged.


    But my OP was asking why they fog when I'm NOT in the car and this unable to use AC. How can I prevent this? Thanks again.
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    hyo silver Awaaaaay

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    You can't, short of moving inland to a drier climate. The car isn't hermetically sealed, so without active conditioning, the inside will be like the outside.
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    GrumpyCabbie Senior Member

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    Sounds normal to me. It's often rainy and damp over here and all my cars have fogged up when it's damp outside. A quick blast of the a/c sorts it out or you could always wind your window down half an inch - at the expense of getting wet!
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    fuzzy1 Senior Member

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    Have you transported any significant amount of water into the car recently, such as from rain-soaked feet, coats, sporting equipment, etc? Spilled any beverages?

    If so, this can take a while to flush out, so you may need to give it an assist -- use fresh air ventilation instead of recirculation when driving, leave windows cracked open when parked (out of the rain), take any wet floor mats out of the car to dry, etc.

    Of course, look for leaks. My old nonhybrid has a serious unidentified leak right now, and it takes several days of active measures, including towels to soak up water from the floor, to dry out.
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    richard schumacher shortbus driver

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    The air gets warm and humid while you're in the car: exhaling, and bringing or allowing in water from the outside. When you leave the car the window glass is the first thing to cool down, so that's where the water vapor condenses. So you must either keep the air dry while you're in the car or remove the humidity the next time you start driving.
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    KK6PD _ . _ . / _ _ . _

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    You could just get a 50 lb. bag of Desiccant and store it in the back...:D

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