Cabin Air Filters: What They Do and When to Replace Them
Your cabin air filter is one of the easiest vehicle service items to forget, largely because you can’t see it. Yet every time you switch on the fan, heater or air conditioning, the air entering the cabin has to pass through it before reaching you and your passengers.
Master Tech Diagnostics Director Tom Shanks with a Ryco cabin air filter, one of the often-overlooked service items that helps keep dust, pollen and other airborne contaminants out of the vehicle cabin.
With spring bringing more pollen and dust into the air, and warmer weather putting vehicle air-conditioning systems back to work, it is a particularly good time to have your cabin air filter checked.
Master Tech Diagnostics and Repairs Director Tom Shanks says cabin filters are easily overlooked because most drivers simply never see them.
“Most customers are very conscious of changing the engine oil and filters, but the cabin filter can quite easily go unnoticed. By the time we remove some of them, you can immediately see how much dust, pollen, leaves and other material they’ve been stopping from entering the ventilation system.”
How a Ryco cabin air filter helps trap pollen before it enters the vehicle cabin.
What does a cabin air filter actually do?
While most motorists understand why their engine needs clean oil and filtered air, the cabin filter has a different job altogether.
“Think of the cabin air filter as the filter for the air you and your passengers are breathing,” Tom explains.
“Outside air is drawn into the vehicle through the heating and air-conditioning system, and before that air reaches the cabin it passes through the cabin filter. The filter is there to trap things like dust, pollen, fine particles and other airborne contaminants.
“Over time, all of that material builds up in the filter. Once it becomes heavily loaded, it can start to restrict airflow through the ventilation system, which can affect how well the heater, demister and air conditioning perform.
“That’s why we recommend having the cabin filter checked regularly. It’s a relatively inexpensive and simple service item, but it has an important job.”
In simple terms, the engine air filter looks after the engine, while the cabin air filter helps look after the environment inside the vehicle.
Ryco Cabin Air Filters are designed to capture airborne contaminants before they enter the passenger compartment through the vehicle’s heating, ventilation and air-conditioning system, commonly referred to as the HVAC system.
That becomes particularly relevant during spring and summer, when pollen levels rise, roads become dusty and the air-conditioning system starts getting considerably more use.
The difference between a replacement cabin air filter and the filter it replaces can be dramatic. A heavily loaded filter has far less capacity to allow air to flow freely through the ventilation system.
How often should a cabin air filter be replaced?
As a general guide, Ryco recommends replacing its cabin air filters every 15,000 kilometres or 12 months, although the vehicle manufacturer’s servicing requirements and individual operating conditions should always be considered.
There isn’t necessarily one replacement interval that suits every vehicle.
A car spending most of its life on sealed suburban roads may have a very different operating environment to one regularly travelling on gravel roads, around construction sites or through dusty rural areas.
Vehicles working in those conditions may need their cabin filters inspected more frequently.
Tom says the condition of the filter itself can often tell the story.
“Replacement intervals are a good guide, but operating conditions make a big difference. If a vehicle spends a lot of time on dirt roads or in dusty conditions, we may find the cabin filter needs attention much earlier.
“That’s why inspection is important rather than simply assuming it will be fine until the next scheduled interval.”
A closer look reveals just how much debris can accumulate deep inside the pleats of a cabin air filter.
What are the signs of a dirty cabin air filter?
Unlike an engine management fault, there usually isn’t a warning light on the dashboard telling you that the cabin filter is becoming blocked.
The clues can be much more subtle.
You may notice:
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- reduced airflow from the dashboard vents;
- the fan needs to be operated at a higher speed than previously;
- the windscreen takes longer to demist;
- an unpleasant or musty smell when the ventilation system is operating; or
- an increase in dust inside the vehicle.
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Sometimes there are no obvious symptoms at all.
It isn’t until the filter is physically removed that its condition becomes apparent. A filter that began life clean and white can emerge carrying an impressive collection of dust, leaves, insects, pollen and general roadside debris.
Old and new side by side. Cabin filters are disposable service items, and once heavily contaminated, replacement is preferable to trying to clean and reuse them.
Can a dirty cabin filter affect the air conditioning?
Yes, although it is important to understand the difference between an air-conditioning system that isn’t producing cold air and one that isn’t delivering enough air through the vents.
A dirty cabin filter does not necessarily stop the air-conditioning refrigeration system from producing cold air. What it can do is restrict the volume of air passing through the HVAC system.
As dust and debris accumulate in the filter media, airflow can progressively decrease.
Tom says that distinction is important when diagnosing an air-conditioning complaint.
“If someone tells us the air coming from the vents is cold but there doesn’t seem to be enough of it, checking the cabin filter is one of the sensible first steps.
“But we don’t automatically assume the filter is the problem. Reduced airflow can also be caused by blower fan faults, air doors, controls or other issues within the HVAC system, so proper diagnosis is important.”
That is why replacing parts based purely on a symptom isn’t always the answer. A proper inspection can determine whether the problem is simply a heavily contaminated filter or something elsewhere in the heating and air-conditioning system.
Tom Shanks from Master Tech Diagnostics installs a Ryco cabin air filter, demonstrating how the filter fits behind the glovebox in many passenger vehicles.
Where is the cabin air filter located?
The location varies between vehicle makes and models.
On many vehicles the cabin filter is positioned behind the glovebox. Others locate it underneath the dashboard or beneath a panel around the windscreen cowl area.
Some are relatively simple to access. Others require trim panels or other components to be removed before the filter can be replaced.
It is also important to fit the filter correctly. Many cabin filters have a specified airflow direction that should be followed during installation.
A heavily contaminated cabin air filter removed from a vehicle. Dust and debris trapped in the filter can progressively restrict airflow through the heating and air-conditioning system.
Are all cabin air filters the same?
No.
A conventional cabin air filter is primarily designed to capture airborne particles such as dust and pollen.
For selected vehicle applications, Ryco also offers its N99 MicroShield Cabin Air Filter range, which uses multiple filtration layers, including activated carbon, to provide additional filtration of very fine airborne particles and help reduce odours.
The correct filter depends on the make, model and year of the vehicle.
Master Tech Diagnostics can identify the appropriate Ryco cabin filter for the vehicle and advise whether an upgraded filtration option is available.
Can you just blow a dirty cabin filter out?
It can be tempting to remove a dusty cabin filter, give it a blast with compressed air and put it back in.
That isn’t the same as replacing it.
Fine contaminants can become embedded within the filtration media, while aggressive compressed-air cleaning can potentially damage the material designed to capture those particles.
A cabin filter is a disposable service item. Once it has become heavily contaminated or reached the end of its recommended service life, replacement is generally the appropriate solution.
As Tom explains:
“A cabin filter is there to collect contamination. Once it has done that job and become heavily loaded, fitting a new filter makes much more sense than trying to get a little more life out of the old one.”
A closer look reveals just how much debris can accumulate deep inside the pleats of a cabin air filter.
Don’t confuse the cabin filter with the engine air filter
It is not uncommon for a customer to say their vehicle’s “air filter” was replaced at the last service.
But most modern vehicles have separate filters doing very different jobs.
The engine air filter filters the air being drawn into the engine for combustion.
The cabin air filter filters the outside air entering the passenger compartment through the vehicle’s heating and ventilation system.
Replacing the engine air filter doesn’t mean the cabin air filter has also been replaced.
Both should be inspected and maintained according to the vehicle manufacturer’s recommendations and the conditions in which the vehicle operates.
Spring is a good time to check your cabin air filter
Spring provides a useful reminder to have the cabin air filter inspected.
Pollen levels increase, dusty roads dry out and the air conditioner begins working harder as temperatures rise.
And if you can’t remember when your cabin air filter was last changed, that in itself is probably a good reason to have it checked.
Ask Master Tech Diagnostics to check your cabin air filter
If your vehicle is coming into Master Tech Diagnostics for servicing, air-conditioning work or diagnostic testing, ask us to inspect the cabin air filter while it is here.
We can check the condition of the existing filter, identify the correct replacement for your vehicle and advise which Ryco Cabin Air Filter options are available.
As Tom says:
“It’s a relatively inexpensive and simple service item, but it has an important job. We’re filtering the air coming into the cabin, so it makes sense to check it regularly rather than waiting until it becomes completely blocked.”
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