If you notice a mildew or mould smell inside your car, it’s often caused by moisture buildup in the air conditioning (AC) system, carpets, or upholstery. While it may start as just an unpleasant odour, mould spores can affect air quality and create health concerns. An inspection helps identify the source of the smell and restore fresh airflow inside your vehicle.

What does it mean if your car smells like mildew or mould?

This smell usually comes from bacteria or mould growth in the AC evaporator, air vents, or damp interior materials. It indicates that moisture is trapped and not drying out properly, allowing mould to form.

Common causes of mildew or mould smells

• Moisture buildup in the AC evaporator or vents
• Clogged or dirty cabin air filter
• Water leaks into the cabin from doors, windows, or sunroof seals
• Damp carpets, mats, or upholstery
• Blocked AC drain hose

Why do you need to fix this problem quickly?

Ignoring mildew smells can allow mould growth to spread, which may affect your health and damage interior materials. It also reduces comfort and can make your car unpleasant to drive.

How do you know when to get it checked?

You should book an inspection if:

• You notice a damp or musty smell when using the AC
• The smell lingers even when the AC is off
• You see condensation, damp carpets, or water stains inside the car
• The cabin air filter hasn’t been replaced in a long time
• Passengers experience allergy-like symptoms while in the car

What happens during an assessment?

A mechanic will:

1. Inspect the AC evaporator and vents for mould or bacteria buildup
2. Check the cabin air filter and replace if clogged or dirty
3. Inspect carpets, mats, and upholstery for dampness
4. Check for water leaks around doors, windows, or sunroof seals
5. Clear the AC drain hose to allow proper moisture removal
6. Recommend cleaning, deodorising, or disinfecting treatments as needed

How much does it cost to fix?

Costs vary depending on the cause. Cabin air filter replacement costs $60–$150. AC disinfecting treatments may cost $150–$300. Water leak repairs or deep cleaning for carpets and upholstery can range from $200–$800+.

Is it unsafe to drive with a mildew or mould smell?

Yes. While not immediately dangerous to the vehicle, mould spores can cause health problems for passengers, especially those with allergies or asthma. It should be fixed promptly to restore safe air quality inside the car.