Most modern cars have a cabin filter, and most owners forget about its existence. Well, until you start feeling a damp and fishy-smelling breeze from the dash vents. It usually gets especially nasty when you switch off the A/C.   

So, what is it and why is its timely replacement important? 

The cabin filter is very much like your vacuum cleaner filter. It prevents any dust and pollen entering the cabin through your ventilation system and keeps the system internally clean. It usually sits between fresh air intake and the heater fan in the dash. 

Aside from the fan the main component of the A/C system that must be kept as clean as possible – the A/C condenser. When the A/C is on, the condenser creates tons of dew. All this water normally is drained through a hose under your vehicle. This is why when you look under a car that sits with an A/C running for a long time you will see a puddle of water. 

If neglected, everything from the outside—leaves, dust, insects, sand, pollen, and pretty much anything you can think of—accumulates on the outer side of the filter. Eventually it rots (the old cabin filter oftentimes becomes so disgusting that its extraction requires PPE). Then it disintegrates and all the dirt ends up being sucked into the system. 

If dust and dirt accumulate on the condenser and its whereabouts, they do two extremely bad things. 

First, they create an ideal environment for bacteria and germs. And this is what makes it smell so bad. And, it’s unhealthy.    

Second, damp dirt plugs, the drain hose, and all the water from A/C operation, rain, or car wash gets trapped and eventually leaks outside. Since it is inside the car, it pours under the interior carpet. 

Modern cars have tons of electronic components and wires down there. As they get wet and rusty, you will inevitably start having strange electrical gremlins, in addition to yet more musty smells and chronically misty windows in cooler weather. And then comes rust, eating into floors… 

Cabin filter replacement may sometimes be rather labor-intensive (and cost more than you might expect). But keeping these filters clean saves you not just your health or good mood from breathing clean and freshly scented air. It saves you thousands on repairs and in vehicle value. Do your math. 


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