The windows are steaming up from the inside
Steaming up of the windows from the inside is a common problem that usually occurs due to high humidity in the cabin or poor air circulation, which not only impairs visibility but also indicates ventilation system issues
Likely causes — most common first
A clogged cabin air filter
A dirty or damp filter prevents normal airflow, causing moisture to settle on the cold glass, which is the most common cause of steaming up, accompanied by weak airflow from the vents
Damp floor mats and sound insulation
In autumn and winter, we bring a lot of water into the cabin on our shoes and clothes, which is absorbed by the floor mats and trim, and when the heater is turned on, this moisture evaporates and instantly fogs up the windows
A broken or stuck air recirculation flap
If the flap that controls air intake is stuck in the 'cabin air only' position, the air is not refreshed, and moisture from people's breathing circulates inside the car in a closed loop
Reduced effectiveness of door seals or drainage
Clogged drainage holes under the windshield or in the doors cause rainwater to seep into the body, and worn-out door and boot seals can also let moisture in
Air conditioning malfunction
The air conditioning works not only as a cooler but also as a powerful dehumidifier, and if it's not working or has drainage issues, moisture remains in the ventilation system
