All of a sudden the interior fogs up (two or three people inside) when the heat control is on the foot symbol and/or on the center outlets in my 2020 Signature. Doesn't do it when set on the windshield symbol. Only takes about 5-8 minutes after starting to drive. Never had this problem before and just started after having my annual inspection by the dealer (no issues). I also just put in a new cabin air filter (arrows pointing down). Never had the issue before. Any ideas what the problem could be?
Why is my interior fogging up? (2020 CX-9)
- Thread starter gphin
- Start date
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- 2009 Mazda CX-9 GT
Turn the a/c on. 
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- 2009 Mazda CX-9 GT
Yes. A/C removes condensation.
Make sure that windshield symbol is always on. You can have foot symbol as well but windshield symbol is a must. With this symbol on - AC is always on by default even if there is no dedicated AC symbol on. Lower outside temps and extra humidity is causing your windshield to fog up.
With only foot symbol you can also switch by accident to inside air circulation which in the end just accumulate more humid air inside the cabin.
With only foot symbol you can also switch by accident to inside air circulation which in the end just accumulate more humid air inside the cabin.
Also, make sure you're not in recirculate mode and taking in fresh air from outside.
I agree, double check recirculation is not on.
Also, AC is automatically ON if you have only the floor vents on or any configuration with the windshield vent on (even if the AC light is not on), however, there is a lower ambient temperature limit which the AC does not turn on.
Not all vehicles are the same, but it's usually in the 35-40F range and below where the AC will not activate.
Also, AC is automatically ON if you have only the floor vents on or any configuration with the windshield vent on (even if the AC light is not on), however, there is a lower ambient temperature limit which the AC does not turn on.
Not all vehicles are the same, but it's usually in the 35-40F range and below where the AC will not activate.
N7turbo
2023 CX-5 2.5T
My AC still works with the heater on at 25F. It doesn't seem to be a panacea, though. I still get fogging, so I have to toggle fresh air whenever I'm not behind a smelly vehicle or not driving past a meat plant.
If your footwell is wet (melting snow or water at your feet) then the ventilation set to your feet will tend to generate a lot of moisture. I noticed it on a previous car where the automatic climate control would always default to the floor vent in the winter. Using any other vent worked and prevented the excessive moisture. Obviously the window vent is the most effective at removing the fogging from the window.
N7turbo
2023 CX-5 2.5T
It's a thing with Mazdas I guess. I never had to do it with any other car. Never had fogging in my Pontiacs so I didn't have to play the game of toggling fresh air on and off 10-20 times on the way to work.
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- ‘19 CX-5 GTR Tu
Might wanna try rain-x antifog . Works really well and I’ve used them in the past on many cars.
Been a few weeks since your last post, how's the fogging?
I was going to ask when the last time you checked/changed the cabin filter. Maybe it was wet/damp and after sitting for a few weeks it dried off.
