Ice on windshield - INSIDE
 

We had some heavy rain and snow here earlier in the week, and I drove my car to and from work all but one day this week.

Last night, it was clear and cold and there was a heavy frost. I had parked outside and needed to scrape the winshield and windows this morning before heading out. On the inside of the windshield, there was also decent coating of frost!? I don't ever recall experiencing such before in any other vehicle. FWIW, the weather was dry and sunny yeaterday and the car seemed dry inside as well - no obvious dampness or moisture source. Any thoughts on what might have caused this interior icing?

On a related but different note, I am befuddled by the heating and ventilation system, but I suppose I need to search the forum a little harder for insight into that topic.

Maybe you are recirculating your cabin air. This may/will frost up your interior windows.

It's quite possible that I am recirculating cabin air. Perhaps there was enough humidity to retain and later freeze the moisture.

My understanding of max defrost is as follows:
Levers between seats up (controls volume of heated fresh air)
Bottom dash lever (red) all the way to right (this lever controls where the ambient air is directed - right=defrost, left=foot wells)
Middle dash lever all the way to right (this lever controls where the heated air is directed - right=defrost, left=foot wells)
Top dash lever all the way left or close to left (this lever controls ambient fresh air from inlet in front of windshield)
All heated air is outside air via the heat exchangers.
Here in Portland Oregon, I can pretty much cook myself out of the car when it is in the 30's outside.

I have heard that keeping a box of baking soda open absorbs moisture, thereby not letting the water vapour settle down on the windshield. It doesn't add any extra odour. You might need to replace the powder when you notice frosting again though.

Levers between the seat - I've only got on lever between the seat (I have it up and I can tell it is providing warm air when car is warmed up and moving). I've also got the dial above with 9 or so numbered positions and a DEF setting. I set it to DEF.

Bottom dash lever (red) - I have it set to the right. However, if I pull it all the way to the left and hold it there, fan or blower speed and air movement ramps up noticeably. If I let it go though, it slips slightly to the right and fan or blower diminishes or ceases.

Middle dash lever - I have this set all the way to the right.

Top dash lever - There are actually two levers here. I have both of them set to the right. Maybe I should set one to the left and one to the right?

That's worth a shot.

frosting, baking soda....what are we doing....baking cakes!

:p

your problem is water inside....check under your carpets for wet spots

I'll take a cupcake with vanilla icing please!:corn:

Yikes, I'd move to where it wasn't so cold.

haha.. funny comments :D

Breathing also causes the windows to fog up ;)

They have Rain-X Anti-Fog http://www.rainx.com/products/Windsh.../Anti-Fog.aspx

Sometimes I actually let some fresh air from the outside ((Top lever just a hair to the right) to help clear up the windshield and that helped.

And to think that I am already well south of the Mason-Dixon line!

So I needed to clean out the car in advance of a PCA autocross event tomorrow (this will be my first autocross!). Anyway, In the process I felt all around the seats, carpets, etc. They all seemed dry. I pulled out the floor mats also, and on the passenger side only, there was a small amount of moisture on the bare floor. It looked like a bit of condensation, as opposed to pooling water from a significant leak. I guess I'll have to keep an eye out on that area and see what happens.

I also re-discovered a card on the inside of the glove box door depicting (in various languages) how to operate the various dash ventilation levers. I noted that what it shows for "max defrost" or whatever is different than what I've been doing with the dash levers. I need to look it over again and tweak the levers accordingly.

I've wondered about trying the Rain-X anti-fog product.

In the meantime, as I mentioned above, I re-discovered the ventilation system instruction card attached to the inside of the glove box door. I need to look it over and get a better handle on the settings.

Did it look anything like this?

Fortunately not!

Great photo though.

i have posted the hvac diagram out of the manual many times . do a search

yup, that passenger floor being wet is more significant than anything else....

I would bet there is more water that comes in...keep that "open" and when it rains go for a drive...bet you see more.

as for the truth about the HVAC controls...move all levers towards the passenger seat = best winter driving I have found

Don't forget to keep an eye out for split hoses. Even a few cracks or splits here and there will add up. I remember when I first got my 911 and was caught with my pants down in the cold and snow without a good working heater system and no snow tires. Probably one of the most miserable experiences I've had. I ended up limping back home with my tail between my legs. I think the worst part of it was that EVERY time I'd hit a puddle or a big flurry of snow, the moisture would get into the heater system and fog up my windows making it even worse.

Double check your heater hoses as moisture can hide in there too if you've gone through puddles and there are splits on the underside hoses. I had moisture issues till I sealed mine up.

Since I replaced all my heater hoses, adjusted the flaps and gone through the condition of the heating system it has gone from a simple cough of warm air in the cabin area to an easily nice and warm cozy feeling in the winter time on the way home.

heater contols
 

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