Start with where it is wet

Feel the carpet and smell a damp paper towel pressed against it. Then use the location to narrow the cause.

  • IfFront passenger footwell, clear water, worse after A/C useThenThe evaporator drain is probably clogged and backing up. A mechanic can clear it.
  • IfFront footwell, water after rain or a car washThenLook at the windshield seal, the cowl drains below the windshield and the door seals. Leaves clogging the cowl are common after fall.
  • IfLiquid feels slick and smells sweetThenThis may be engine coolant from a heater core leak. Stop driving it far and see a mechanic; coolant is toxic.
  • IfRear footwells after storms, car has a sunroofThenSunroof drain tubes run down the pillars and can clog or disconnect, sending water into the floor.
  • IfOnly the driver's side, especially in winterThenSnow and slush carried in on boots may be the whole story. Rubber all-weather mats usually solve it.
Air movers and dehumidifiers seen from above on a bare subfloor

Air movers and dehumidifiers seen from above on a bare subfloor. Included to show the kind of work involved, not a property or job connected to this site.

Why speed matters

Under most automotive carpet sits a thick pad of jute, felt or foam that soaks up water and releases it slowly. A footwell can feel only slightly damp on top while the pad underneath is saturated. In a warm, closed car, mildew can begin growing on wet organic material within a few days. Once it does, the smell spreads through the cabin and the ventilation system can pick it up.

Colorado's low humidity helps, but it does not dry a pad trapped under carpet and a rubber mat. Many Aurora owners find the problem only after weeks of foggy windows or a musty smell that they first blamed on the A/C.

Common leak sources and how to test them

Suspected source
Evaporator drain
Simple test
Run the A/C on a humid day and look for dripping under the car
Usual fix
Clear the drain hose
Suspected source
Cowl drains
Simple test
Pour water slowly into the cowl below the windshield with the hood up
Usual fix
Remove leaves and debris
Suspected source
Door seals
Simple test
Hose gently along the door edge while someone watches inside
Usual fix
Reseat or replace the seal
Suspected source
Sunroof drains
Simple test
Pour a little water into the sunroof channel and see where it exits
Usual fix
Clear or reconnect the drain tube
Suspected source
Windshield seal
Simple test
Hose along the top and side edges with doors closed
Usual fix
Reseal by a glass shop

Drying once the leak is fixed

  1. Pull up the carpet where you can

    Removing sill plates and lifting the carpet edge lets air reach the pad. Sometimes seats need to come out for full access.

  2. Extract standing water

    A wet-dry vacuum pressed into the pad removes far more than towels.

  3. Dry with fans and low humidity

    Fans and a dehumidifier in a closed garage, or warm dry days with doors open in a secure spot, work best.

  4. Clean for odor last

    Once fully dry, clean and deodorize the carpet. If the pad smells musty after drying, replacing it is often simpler than treating it.

General information for Aurora, not a quote or professional advice. In an emergency, call 911.