Windows Fog Up Inside
The inside of your windows fogs up, especially in cool or humid weather. This is a humidity problem usually tied to the AC, cabin filter, or a coolant leak.
Find a TechnicianCommon causes
- AC not dehumidifying (low refrigerant or off)
- Clogged cabin air filter
- Blocked AC drain leaving moisture inside
- Heater-core leak fogging the glass (sweet smell)
- Wet carpets or trapped moisture in the cabin
Frequently asked questions
Why do my windows fog on the inside?
Warm, humid cabin air condenses on cool glass. Running the AC (which dries the air) usually clears it; if it doesn't, something's keeping moisture inside.
Could a coolant leak cause foggy windows?
Yes — a leaking heater core can fog the windshield with an oily film and a sweet smell, which needs repair rather than just defrosting.
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