A musty smell after rain usually comes from moisture and dust inside the aircond: a damp cabin filter, and mould on the cold, wet evaporator behind it. Replace the cabin filter if it is dirty or damp, switch the aircond compressor off and run the fan for the last few minutes of a drive to dry the system, and check for wet carpets. If the smell keeps coming back, have a workshop clean the evaporator.
Where does the smell come from?
Behind the dashboard, the aircond blows air through two parts: the cabin filter, which catches dust and leaves, and the evaporator, a small radiator-like coil that cools the air. The evaporator is always wet when the aircond runs: moisture from the air condenses on it and drips out under the car through a drain pipe.
A wet surface plus dust plus heat is exactly where mould and bacteria grow. When the car sits in the sun after a drive, that damp layer warms up, and the next time you switch on the fan, you smell it.
Rainy weeks make it worse. The air is more humid, the filter stays damp, and water finds its way into the car on shoes, umbrellas and wet clothes.
What is causing yours?
| What you notice | Likely cause | What to do |
|---|---|---|
| Musty smell for the first minute, then it fades | Damp dust in the filter and on the evaporator | Replace the cabin filter; dry the system before parking |
| Musty smell that stays the whole drive | Mould on the evaporator | Workshop evaporator cleaning |
| Smell worse after heavy rain, damp floor carpet | Water getting in, often through blocked drains under the windscreen or a door seal | Clear leaves from under the windscreen panel; have leaks checked |
| Water dripping inside the car, under the dashboard | Blocked aircond drain pipe | Workshop: clear the drain |
| Sweet, syrupy smell | Possible coolant leak | Workshop check soon |
| Burning plastic or electrical smell | Possible electrical fault | Stop and have it checked |
Habits that help
- Dry the system before you park. For the last few minutes of a drive, switch the aircond compressor off (the A/C button) and leave the fan running. The air dries the evaporator so it isn’t left sitting wet.
- Don’t leave wet things in the car. Umbrellas, raincoats and wet mats keep the cabin humid.
- Keep the area under the windscreen clear. Leaves block the drains there, and the water can end up inside.
- Replace the cabin filter on time, and sooner after a haze spell or weeks of rain. A damp, dusty filter is one of the main sources of the smell.
Will a new cabin filter fix it?
Often it helps, especially if the old filter is grey, full of leaves or damp. The DuraFit cabin filter pack lists Blocks PM2.5 Dust, Strong Airflow and Anti-Mould & Moisture Resistance.
But a filter can’t clean what is already behind it. If the smell is back within days of a new filter, the evaporator needs cleaning. Workshops do this with a cleaning foam fed into the aircond housing or through the drain, without taking the dashboard apart.
When should you see a workshop?
- The musty smell comes back within days of a new filter.
- You find water on the floor, or the carpets stay damp.
- The smell is sweet, burning or like petrol.
- The aircond also blows weaker or less cold than it used to.
Any ServAuto workshop can check the filter, the drain and the evaporator in one visit.
Finding the right filter
Cabin filters are made for specific cars. Look up yours in the DuraFit catalogue, or see all DuraFit cabin filters. Car not listed? Send the make, model and year to the ServAuto BD team on WhatsApp.
Frequently asked questions
Is it normal for the aircond to smell when I first switch it on?
Do aircond deodoriser sprays fix the smell?
Should I drive with recirculation or fresh air when it rains?
Which DuraFit cabin filter fits my car?
Sources
- Your vehicle's owner's manual (air-conditioning operation and cabin filter replacement).
- DuraFit cabin filter packaging (pack claims quoted word for word).
- DuraFit catalogue: cabin filter part numbers and fitment, durafit.my/catalogue.
