First time on the forum. I have a 2005 325xi with 100,000 miles in Michigan. The car was in the driveway twice this winter and both times the windshield and rear window ice over. It's like a thin frost, I have to scrape the windows inside to be able to see out of them. I have tried to run air conditioning while driving but they frosted back over again. I can't see any window or door seals that look damaged either. I have other cars outside as well without problems. Thank you in advance for any help. - Mark
hmm... given how my old storm windows frost over in sub-freezing temps from the humidity maintained by my furnace humidifier, I'd have to guess what you're seeing means the air in the car is also humid enough for the same thing to be happening as I see with my storm windows. With that degree of frost, I'd be guessing that much moisture means something's leaking and you have some water sitting in the car. 2005, should be E46, which means spare tire I think, pull your trunk floor cover and the side trunk covers and see if there's any water back there. Feel the carpet in the passenger compartment, see if that's all dry. In very cold temps, I've had a few breaths frost on the inside of the front window, but that's nothing like what you're talking about. I'm not sure if underneath the E46 rear seat it's just sheet metal or not - some BMW's have space under the seats where water could sit. Air conditioning works to remove humidity which is why it can help to clear windshields, obviously you're not having any luck with that. When you start the car, make sure to direct the air appropriately - hit the defrost button, which should direct all interior cabin air to the vents at the front of the dash and onto the windshield. You'll have to put up with the footwell being cold until the car gets completely warmed up - set the controls manually, don't use the 'auto' setting - have the fan on full blowing the air to the upper vents (which is what defrost setting should do), and when it's blowing hot air, hit the down button to direct air the footwell. The button that pushes air to the center dash vents (the ones that blow directly at your face) should be off. Close the dash vent louvers also, and turn the slider knob to red (which directs coolant so the dash vents can blow hot if desired). Closing the louvers would help, nominally, maximize the air flow to the windshield & footwell. Turn on the rear defroster also, and if it automatically turns off after awhile, turn it back on and repeat to keep it on. Obviously, make sure the temp controls are turned to maximum heat. Unless you have a short drive, once the car engine is fully up to temperature, eventually blowing max heat into the cabin should just about have you sweating. Moisture condenses more easily on a dirty windshield - might be in a cold spell at the moment, but when the weather allows, clean the inside of the windshield so it's completely shmootz-free - no smudges, smears, etc. I think you can run the a/c with the heat on full and still have some dehumidifying effect - using the heat on full may be more effective, though heat only may take longer to clear the windshield. I usually find the a/c, unless it's summertime, doesn't necessarily keep the windshield clear, at least turning it off after awhile in the winter - heat usually does unless it's really, really cold (so cold that you're at the limit of what the car's heating system can counteract). If you're not getting full hot air blowing into the cabin with the temp set to max heat, then there's some sort of heating/cooling system problem - obviously without full heat being delivered, you won't be able to essentially boil/burn off excess moisture. When driving in winter, it's best to have the air going to the windshield and footwell which serves to warm the whole car and keep the windshield clear. Having the dash vents on blowing warm air on your face or hands means there's less to keep the windshield clear. I'd say also buy two 3-packs of these, or at least one 3-pack, and put them in the car. Put 3 in the trunk and 3 in the cabin, to help absorb the humidity. Would seem likely something's leaking into the trunk or cabin, someplace. https://www.griotsgarage.com/product/storage desiccant bags.do
Normally see this from a water leak into the vehicle making the carpets wet. Check carpets and if you find one wet the vapor barrier behind the door panel may be causing the water leak.
