My windows fog up in the rain and won't clear
The defrost uses your AC to pull moisture out of the air, so weak AC means slow defogging. Other causes are a wet carpet from a leak, a clogged cabin filter, or the system stuck on recirculate. A greasy film that smells sweet points to a heater core leak.
Urgency
This week is fine
What to do right now
What to do right now
- 1Set the defrost to fresh air, not recirculate, and turn the AC on with it.
- 2Feel the floor mats and carpet for dampness. A wet carpet keeps fogging the glass.
- 3Clean the inside of the windshield. A dirty film fogs faster.
- 4Pull over if you cannot see. Driving blind on I-95 in a storm is not worth it.
What it usually is
What it usually is
AC repair
If the AC is weak, the defrost cannot dry the air. Fixing the AC fixes the fog.
See the serviceCooling system
A leaking heater core puts coolant steam into the cabin and leaves an oily fog on the glass.
See the serviceCar diagnostics
We find where water gets in, from door seals, a sunroof drain, or a clogged AC drain, and check the fresh air and blend doors.
See the serviceQuestions people ask
Why do my windows fog on the outside?
When the AC is very cold and the air outside is hot and wet, fog forms on the outside of the glass. Use your wipers and ease off the AC a little. It is normal in a Miami summer.
Should I use recirculate or fresh air?
Fresh air when fogging. Recirculate keeps the same wet air inside the car and makes the fog worse.
My carpet is wet after a heavy rain. Is that related?
Yes. A wet floor adds moisture to the cabin all day. If water came in over the door sills on a flooded street, tell us. That needs a full dry out and an electrical check.
Does the rear defroster use the AC too?
No. The rear window uses heating lines in the glass. If those stop working, it is usually a broken line or a fuse.