Fogging windshield

Fogging means moisture is in the air you are blowing against the windshield. Warming the air helps some but then warmer air holds more moisture, too. Typically the A/C gets turned on a bit when you use the Defrost/Defog setting because the A/C dries out the air. My A/C stopped working years ago due to a leak which wasn't detected due to long-time non-use which resulted in damaging several components which made it too expensive to repair. Ever since then, defogging the windshield takes longer (higher fan setting, clearing the snow from the vent beforehand, waiting for the heater core to provide heat to the air) because the A/C isn't helping to dry the air.

Does your A/C work? It's been too long but I recall that the A/C isn't set to full on when in the defrost setting so maybe it doesn't work well at low load (so maybe you need it recharged). Are you cleaning out the intake vent atop the hood near the windshield so you aren't sucking in snow? Do you even have snow in your area? If it is foggy outside then the air you suck in is wet, and the A/C helps dry it out. I thought the A/C was supposed to come on a bit when in the defrost setting. Maybe not in your model which means you need to manually enable the A/C to dry the air. Blowing humid or wet air against the windshield is obviously not as effective as blowing dry air at the windshield regardless of the temperature of the air.

No there is no snow here and hardly any moisture in Orange County. Dry as a bone; that's why we're prone to fires.

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Ever notice a sweet smell in your car - like toasted marsmallows? perhaps you have a leak in the heater core and coolant is causing the problem?

Carl

Switch your selector from "recycle" to "fresh" air.

Check and see if you have a water leak in your heater. That happened to me several years ago and the windshield would fog really, really bad.

Don

My 2K outback has always been a lousy windshield defroster. Even with the AC on High. Just not quite enough air. I lived in Orange County and I know you can have some superior fog in the mornings this time of year. I wouldn't be surprised by a defrosting deficit...Cheer up, though,....other than that, I love the car!

Jim L.

My STi seemed to have a much worse fogging problem than I'd had in other cars. I used some of that Rain-x stuff they sell for putting on the /inside/ of the windows and that cured it nicely.

-- Mark

Just another thought, if the output seems low, perhaps your car has a cabin airfilter that needs changing.

I dunno

Carl

1 Lucky Texan

It's also possible that the inside of your windshield is dirty. Sometimes, there is a type of dirt that shows up as fog.

Try cleaning it with window cleaner.

After cleaning, you can "wax" it by spreading a very thin layer of bath soap. This prevents the collection of outgassed plastic from your dashboard.

I will bet serious $$ that this is the OP's problem. Now if I can just get my SO to clean HER Suby's windshield with this fogging problem....

Thanks everyone for all the ideas. I've never had to top off my coolant level so I don't know if that proves whether there is no leak or not. I've never had any odd coolant smells inside the car. I'll check the filter and clean the windshield on the inside.

Adam

Here in NW FL cooler outside temps and hi humidity can cause rapid fogging of windshield. Switching to defogger (A/C cuts in here) can aggravate the problem as A/C further cools the glass. It makes sense then to add a little heat when switching to defog, adding or subtracting heat as required.

Rich

I do just the opposite, and I never have had a problem. My theory is that if you recirculate cabin air, the air conditioner will dry it out. If you bring in fresh air, you will bring in moisture with it, so the air conditioner has more moisture to deal with.

I wonder why the owners manual specifically says not to use the defrost with the recirculate as it causes the car to fog up???

Its a balancing act. If one or more sweaty people with snow covered boots are in the car for a long time, the internal humidity could be higher than the humidity outside, so external vent would actually clear out some humidity. Often extremely cold air is quite dry - so that would be beneficial. But there are occasions when the outside conditions are cool and 'muggy', or, after a night of disuse-the inside of the car may initially be muggy. Under those conditions, running the a/c compressor and the vent set to recirc. would more quickly clear the windshield. Even in summer, the inside of the car can become dry enough to irritate eyes and switching to 'vent' occasionally will allow some moist (relatively) air in - at the expense of more heat.

Carl

Humans are a prodigious source of humidity. Several times a minute we inhale more than a liter of air and exhale it at more than 90 degrees F and nearly

100% humidity. During winter the cold air has very little moisture, because it just can't hold it. After all, that is how the A/C dries the air - it makes the air too cold to hold much moisture.

A window that is completely unfogged in the winter fogs immediately if we breath anywhere near it.

Mike

So it's a cold morning and I've just started the car, turning on the Defrost at the high heat setting to clear the windshield and warm myself up as well. I've just turned on the A/C ? ?

Yup.

Unless you go into your HVAC controls, and detach the microswitch (single screw) that's depressed when you rotate the controls over to "Defrost" position.

Most all cars use that mode, btw.

Yes, and that's actually a good thing. And you can turn the heater setting to provide heat, and you'll be mixing refrigerated air with heated air, and that's OK, too.

In this case, the car engineers really know what they're doing.