fogged up windshield

I parked my car for dinner over the weekend and it stopped raining for a while. I got back to my car and just the front windshield was fogged up (not just a bit but totally covered on the inside). No other cars in the parking lot were fogged up though? I also notice when I drive the windows fog up quite easily in this car. Anyone notice the same thing and is there anything to prevent this other than keep a window slightly open? My Audi and BMW have that venting thing (forgot what it's called) that circulates air when the car is parked - does anyone know if the 996 C2 has this feature too?

I've had good results on moist days by doing the following. Turn on recirculation, wait a few seconds and then lower the fan speed all the way to "off". I do this just before turning off the car and it seems to close up the car to outside elements pretty well.

Have you checked your carpets to see if they are wet any where? Excessive moisture in the car (causing the window fogging) may indicate blocked sunroof drainage hoses, and a water leak into the car. Or - have you cleaned the inside glass of the windshield recently? - out-gassing from interior surface cleaners (like dashboard cleaners) causes contamination of the glass surface, and this allows condensation to collect more easily in the right conditions. Clean your interior glass to remove the problem.

Your automatic climate control system runs the A/C compressor all year around, mostly to attain the best airflow human comfort level via reheat/remix method. But also for dehumdification during cool and cold climate periods and during the summer for cooling and dehumidification. The result of that is that any time you shut the system down the A/C cooling evaporator will very likely be saturated with moisture, a thin film covering the entire ~10,000 square inches of evaporator vane surface area. Now, with the system stopped, the evaporator surfaces will begin to warm to the temperature of the cabin and that moisture will begin to evaporate. Convection flow is UPWARD toward the cool or COLD interior windshield surface. My solution was to add a small toggle switch mounted inside the center console glovebox that I use to open the A/C compressor clutch circuit throughout the winter months unless I actually need cooling capability.

So, on a spring day, when the outside temp is low 40's, and the climate control is set to 70 degrees--the heat, AND the A/C compressor will always be running? Doesn't that rob HP? There's no way of just having heat on, and not running the A/C?

I fogged up my windows only once in this car and boy was she and I sore the next day. When it's humid outside and I have the "AC" blowing on the windshield before parking the residual air fogs up the windshield once parked.

Thanks for the replies guys. I don't seem to have any leaks - no moisture anywhere in the car. I haven't cleaned my car yet - was detailed when I purchased it so the dash cleaner may be doing this as cdodkin suggests. Wwest - thanks for the info on the A/C - I always thought it was odd that once I hit the defog on my C2 or A4 the air con comes on too. I figured the heat should just be running to clear up the fog. The thing that was odd to me was all other cars in the lot weren't fogged up - just mine was..? I'll try cleaning the windshield, recirculating the air before shutting down and seeing if that works - just a pain to sit there and wait for the defog to do it's job when I could be drivin!

For a more detailed explanation and a possible solution go to airsept.com and read up on their EED, Electronic Evaporator Dryer.

Yes, if there is any one thing that ALL of us could do to improve FE nationally it would be to disable the A/C except for initially cooling the cabin down to your comfort zone and/or keeping it cooled down when the climate requires it. A few years ago the left front radiator/condensor cooling fan failed while driving across AR in 100F+ August day. That resulted in not being able to use the A/C without overheating the engine every time traffic slowed or backed up due to construction. After enduring the HEAT for more miles than I like to think I realized that I could make the A/C a LOT more efficient by bypassing the system's reheat/remix mode. So I turned the temperature setpoint down to max cooling and then used the blower motor speed to regulate our comfort level. Somewhat discomforting COLD system airflow but not nearly as bad as windows down and 100F+ airflow with 90% Rh Drove all the way home to Seattle that way in reasonable comfort.

Not sure if this would help but have you tried cleaning the windows? Dirty windows seem to fog up a bit easier...