Cabin filter replacement

Signs the filter needs changing

The filter clogs gradually, so the change is not always noticed. Signs include:

• The airflow is weak even with the blower on full.
• The windows fog up easily and the windscreen clears slowly.
• A stale or musty smell comes from the vents when you switch on the blower or the air conditioning.
• Dust builds up on the dashboard and around the vents faster than usual.
• Pollen allergy symptoms get worse in the car in the spring.
• Bits of leaves or other debris blow out of the vents.

Other faults can cause similar symptoms. If the blower does not turn at all or works only on its top speed, the fault is usually in the blower or its resistor. A whining blower is often worn, and a rattle usually means leaves have got into the blower. If the smell stays after a new filter, it often comes from the air conditioning evaporator. So we look at the old filter and test the blower before we suggest any other work.

Cabin filter replacement interval

The interval is set by the car's manufacturer and written in the service book or the service schedule. In most service schedules the filter is changed every one or two years, usually with the scheduled service. Some manufacturers also give a kilometre limit, and then the change is made at whichever comes first.

Driving conditions often matter more to the filter than kilometres do. In the capital region the spring street dust clogs the filter quickly, and in the autumn leaves collect in the fresh-air intake under the windscreen. If you drive a lot in town or on gravel roads, or you have a pollen allergy, the filter is worth changing once a year, even if the service schedule allows a longer interval.

Electric cars have a cabin filter too. In an electric car it is often the only filter changed regularly, because there is no engine air filter and no oil filter. The filter can be changed at the same visit as a scheduled service or an air conditioning service.

Standard or activated carbon filter

A standard cabin filter catches dust and pollen. An activated carbon filter also has a carbon layer that binds odours, including the smell of exhaust in traffic jams and tunnels. It costs more than a standard filter. For some cars there are also multi-layer filters, which their makers say also filter out fine particles or allergens. We tell you which filters are available for your car, and you choose.

How the change is done

1. We check where the filter sits in your car and which filter the manufacturer specifies. Some cars have two filters.
2. We open the filter housing. Depending on the car, we remove the glove box, the lower dashboard trim or the cover of the housing under the windscreen.
3. We take the old filter out and see how dirty it is. We vacuum leaves and debris out of the housing so that they do not end up in the blower.
4. If the filter sits under the windscreen, we also check the fresh-air intake and the scuttle drain holes. When a drain hole is blocked, rainwater can rise in the scuttle and run into the ventilation and the footwell.
5. We fit the new filter with the arrow on its frame pointing in the direction of the airflow, and close the housing tightly. A filter that sits badly lets dust past it.
6. We test the blower at every speed, in fresh-air and recirculation mode, and check that air comes out of every vent. Finally we record the change in the service book.

How long it takes

Where the filter sits behind the glove box, the change often takes only about a quarter of an hour. It takes longer if the dashboard trim or the cover of the housing under the windscreen has to come off, or the housing is full of leaves. Even so, on most cars the job is done in under half an hour. We tell you the expected time when we agree the booking.

What the price of a cabin filter replacement depends on

The price depends on:

• The type of filter. An activated carbon filter costs more than a standard one, and multi-layer filters cost the most.
• Where it sits. A filter behind the glove box is changed quickly. If trim or the cover of the housing under the windscreen has to come off, there is more work.
• How many filters. Some cars have two filters, and both are changed at the same time.
• The parts. Original and aftermarket parts differ in price. We tell you which part we use.
• The state of the housing. If the housing holds a lot of leaves or mould, cleaning it takes time.

We check the car and tell you the price before the work starts. If the filter is changed with a service, no separate visit is needed.

The cabin filter and the inspection

The cabin filter is not checked at the inspection, but the windscreen demisting is. Under Traficom's inspection regulation, the windscreen equipment covers the wipers, the washer and the demister, and the inspector tests whether they work. If a device does not work at all or is missing, the car fails. A weak one earns a repair notice.

In Traficom's statistics for 2025, 3 687 rejecting faults and 93 481 repair notices were recorded for the windscreen and its cleaning equipment. The statistics do not say how many of them concerned the demister. A clogged filter weakens the airflow, but rarely so much that the demisting stops altogether. If the demisting does not work at all, the cause is usually the blower, its resistor or a fuse.

What you can check yourself

• The service book. See when the filter was last changed. If there is no entry, the filter is worth changing.
• The filter's condition. The owner's manual says where the filter is. If it sits behind the glove box, you can often look at it yourself. If the filter is grey or black or has leaves in it, it is due for a change.
• The fresh-air intake. Clear leaves and snow from the grille under the windscreen. When the windows fog up, keep recirculation off. With recirculation the damp air keeps circulating in the car and is not replaced by outside air.
• The airflow. Put the blower on full in fresh-air mode and feel the flow from the vents. If it has weakened over time, the filter is often the cause.

Many owners change a filter that sits behind the glove box themselves. If you do, check that the arrow on the frame points in the direction of the airflow and that the housing cover closes properly.

When not to drive the car

A clogged filter alone does not stop you driving, but poor visibility does. Do not set off if

• the windscreen is fogged or iced and the blower cannot clear it
• smoke or a burning smell comes from the vents
• an oily film forms on the inside of the windscreen and the car smells sweet.

A burning smell can come from an overheating blower or its resistor. Switch the blower off and call us. A sweet smell and an oily film can mean that the heater core is leaking coolant. Check the coolant level and call us, and we will agree whether the car can be driven to the workshop.