MVDESQ

I have a 2009 Boxster and when the temperature drops the windows fog up even with the ac on and with the ac on with recirc. How do I prevent this? The defroster takes the fog away but we cannot drive the car with the defroster on the entire time. Thanks in advance.

Macster

Do you see the snowflake symbol light up when the A/C button depressed?

Do you feel warm/hot air flowing from the defrost vents, primarily at the intersection of the dash top and the windshield, but warm air from all the vents?

If the A/C doesn't actually come on -- although in real cold temps (32F or thereabouts and colder the A/C will not be turned on to avoid freezing the evaporator -- or for some reason warm air does not flow out the vents, there is a problem with the air flaps or air flap vents or the A/C control to name a few possible cause of this symptom.

If the A/C snowflake comes on when you press the A/C button and warm air flows from the vents (after the engine has a few moments to warm up after a cold start) then the evaporator drain may be blocked and the moisture is coming from this area or there's possibly a leak with the heater core. In the case of the heater core leak I think you'd detect the odor of anti-freeze, though.
Also, the coolant level would be down.

Be sure you check the water drains under the plastic panels under the front trunk lid, the panels on either side of the battery cover. If they are plugged water can collect and this can result in excess moisture being in the air drawn into the cabin.

While you're there check the cabin air filter is installed properly and not damp.

Unless the moisture is coming from backed up water drains or from an improperly installed cabin air filter the other possible causes will almost certainly need professional mechanic attention.

If the car is under warranty then all you need do is drop the car off at the local Porsche dealer service department and provide the details of your complaint.

Sincerely,

Macster.

No HTwo O

Turn recirculate off.

Dr.Bill

Why not? Isn't that what it's for?

I used to keep it on all the time when I lived in Minnesota, Wisconsin, and upstate NY. Then I got smart and moved to a warm climate! Not even sure where the defroster switch is now!

Marine Blue

That's what I was thinking too. Recirculate is nice when it's hot out but can cause humidity issues in the cabin on cooler/rainy days.

Macster

Oh, yeah, recirc mode will do it. Missed that. Good catch.

Sincerely,

Macster.

MVDESQ

My fogging issue occurs regardless of whether or not recirculate is on or off.

Macster

Then the items I raised in an earlier post do apply, at least are things to consider.

Sincerely,

Macster.