Not sure if this matters, but I have a a 1990 Acura Integra with a sunroof. As far as I know and can tell, the door and window seals are in good shape despite the car’s advancing age.
So every morning in the autumn/winter, or whenever it’s cold, I usually find my windshield either steamed up or wet on the inside with condensation. Similarly, when it’s cold or rainy, the interior steams up quite a bit, and I’m usually pulling over to wipe down the windshield or driving with the windows down (brrr!). Even this isn’t particularly effective.
I also have a dicky defroster - it works when it feels like it, and even going full blast when it does decide to work, it often only takes care of the bottom quarter of the windscreen. Something tells me there’s some thermodynamic principle at work that I’m ignorant of, and there has to be a solution other than grabbing a wad of paper towels every morning and spending ten minutes wiping the windows down… from the inside. I even had the Safelite people come to inspect my windshield to see if there was a leak in the window seal that allowed the water/dampness to get in… they couldn’t find anything. However, I do notice water dripping on the floorboard on the passenger side if it’s raining really hard.
So have others encountered the same problem with their cars? If so, how did you address it?
Rain-X makes an anti-fog product you can rub on the inside of your windshield. That cuts down on garden-variety condensation. If you have something more complicated going on, like a leak, it may not be enough to do the trick, though.
There is nothing thermodynamic about it, there is too much water in your cabin. Find and clear the drain tubes. If that doesn’t do it, pick a dry day, sit in the car, and have someone go to town with a garden hose. Check to see if there is water coming in anywhere, check the trunk, too.
My bet is that your heater core-A/C evaporator box drain is plugged, so when you ask for defrost, all of that standing condensate in the box gets blown onto the inside of the windshield. Somewhere on the firewall side of the engine compartment, perhaps towards the lower edge is a rubber hose with a little one way valve in it. The valve is plugged with muck. Popping it out and cleaning is a 5 minute task-finding the bugger may take an hour.
It’s been some time ago, so I don’t remember the exact details, but I had the same thing happen in my car.
My friend showed me a small symbol of a car on the dash at the environmental controls section, with an elipitcal symbol “on” the car image. He explained that you can get your air ‘recirculated’ or essentially from outside. He pressed the symbol and the problem went away immediately.
I’m wondering if that is the issue.
If you’re introducing warm/humid air from outside into the cabin, it will quickly fall below dewpoint and condense on the windows.
Does your car have such a symbol? If so, press it! I’m guessing that your percentage of outside air is too great and you’re introducing warmer or humid air into a cooler environment–and so, condensation.
Previous answers pretty well cover the bases. To summarize:
You could be getting excess water ingress through a leak in the windshield molding or from the fresh air intake if its drains are clogged. This could explain the dripping you see. The water hose test should show if this is the case. Spray it all around the edge of the windshield and through the air intake grill at the base of the windshield. While the sunroof and its molding are also possible leak sources, presumably you would know by water dripping on your head.
You could be retaining excess water in the A/C evaporator if its drain tube is clogged. This could also explain the dripping you see. It’s not unusual for this to occur. Prior to pulling the hose off the drain spout (under the dash on the passenger side, close to the firewall) get something to catch the water, such as a tinfoil chute leading to a shallow drain pan. The clog is usually in the drain spout (part of the evaporator case) rather than in the plastic hose. You’ll probably have to make a declogging tool out of wire that you can shove into the drain spout to loosen and fish out the clog.
You could be keeping moisture in the car – including that from your breath – if the air intake mode is set on recirculate instead of outside. This is not unusual. Most people have never read their owner’s manual and don’t understand this feature. Use recirculate only for getting the coldest air conditioning, and for temporarily blocking outside air when going through a very dusty area or a “skunk-smell” zone or somesuch.
I think you’re getting mixed up here. Outside air in this weather is not going to be warmer than inside air. The warm, humid air that causes this type of problem comes from people’s breath. If the intake air mode is set to recirculate, all that moisture builds up in the car. You want the mode set to fresh air intake so that the airflow draws moisture out of the car.
The aircon should dehumidify the air whether the source is external or recirculated. I’ve found that leaving the aircon on recirc is not a good idea, as the air soon becomes very stale and almost headache-inducing. But momentarily useful for driving downwind of landfill sites and sitting behind an old diesel smoker in a traffic jam.
The screen blower only demisting the bottom of the screen is just down to shit design. The air is hitting the screen at too steep an angle. Mazda 323s do this, with the added bonus of something in the aircon pipes smelling faintly of wrestler’s jockstrap.
Check for moist carpets in the vehicle too. Sometimes a hole in the wheel arch or bulkhead will let in water from road spray, and this will make the interior very humid. I had an old Austin Maxi like this, and every autumn would see a little crop of toadstools growing out of the carpet near the clutch pedal.
No problems with my current Citroen. The front windscreen demist button turns on the aircon and directs all the air at the windscreen. Even if the air is cold, it still demists the windscreen in a few seconds just because of the low relative humidity and high flow rate. It’s magical to behold.
Take a white paper towel or cotton rag. Wipe the interior glass surface.
If you are getting an oily substance (possibly with a green tint) off the glass, your heater core is leaking and your defroster is blowing a fine mist of coolant (antifreeze) onto your windshield. Left unattended for long, you will also find staining under the carpet on the right (passenger) side or near the center console if you have one. Good luck.
Top tip from LucyInDisguise. I had this very thing happen on an old car of mine - every now and then a little wisp of smoke would waft up from under the windscreen, and I was sure it was a shorted wire. Smelled just like burnt insulation. As it happens, it was a leak in the heater matrix, and the smell was the smell of old coolant, which became apparent when I opened the radiator cap when warm. I bypassed the heater matrix once I sussed it, but the damage was done. Shortly thereafter my big end seized up, probably caused by localised hotspots due to air pockets in a leaking cooling system.
Before you park and lock up your car for the night… Open all of the doors for 3 minutes to change out the warm humid moist air accumulated on your way home.
Close up and lock the car for the night. At the end of the week report back on the conditions in the mornings!
