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Car Maintenance 101: What is a Cabin Air Filter & When Should You Check Yours

Yeah, consider this one clogged. Read the full story below. (Image/Kyle B.)

This story begins with a burned-out blower motor in Kyle’s new car.

Kyle’s a friend of OnAllCylinders and a really smart car guy, so he quickly dove in to investigate. What he found was a severely clogged cabin air filter, packed with debris, insulation, and grit. That meant his climate control system’s blower motor was working overtime to move air, and that extra strain hastened the blower motor’s demise.

Suffice it to say, Kyle’s experience gave us a good reason to write an article on cabin air filters.

What is a Cabin Air Filter?

Cabin air filters showed up on luxury cars near the end of the 1980s. The filter technology quickly moved mainstream and, by the mid-2000s, you could find cabin air filters in pretty much every North American market automobile’s climate control system.

So if your car was built in the 21st century, there’s a good chance you’ve got a cabin air filter. (And if you’ve never inspected it, now would be a really, really good time…but we’ll get to that in a sec.)

A cabin air filter is an air filter that’s located just upstream of your vehicle’s HVAC blower motor. The blower motor pulls dirty, outside air through the filter, on its way into the climate control system, and out into the passenger compartment.

The cabin air filter removes dust, road grit, and other particulates so the vehicle’s occupants can breath fresh, clean air. That can be especially beneficial for passengers with allergies, asthma, or other respiratory concerns.

Problem is, the filter element will gradually clog up, so you need to replace it regularly.

Where is My Vehicle’s Cabin Air Filter?

While all vehicles are different, the most common places nowadays seem to be tucked in behind the glove compartment or stuck up near the center of the dash. But depending on your car, SUV, or truck, it may be somewhere else—we’ve even seen them under the cowl at the base of the windshield (accessible by popping the hood).

Here’s the cabin air filter location for a 2004 B15 Nissan Sentra, right behind the glove compartment. You can see the filter sits directly on top of the HVAC system’s blower motor. Outside air is pulled in via an exterior vent in the windshield cowl, down through the air filter, past the blower motor, and into the car’s HVAC system. (Image/OnAllCylinders – Paul Sakalas)

The good news is, cabin air filters seem to be getting easier to service. What used to be a 30 minute affair that involved some prying and pulling, is often now just a matter of a few minutes with the removal of some basic plastic retaining tabs.

For instance, we replaced the cabin air filter on a 2004 Nissan Sentra. It was tucked behind the glove compartment, yet only required us to pull out a few plastic pins on the glove box door, remove four screws for the inner liner, and pop off the lid for the air filter housing. All told, less than a five minute job. We’ve had similar experiences with other late model cars.

A quick online search on your specific vehicle’s year, make, and model will likely reveal a tutorial video or PDF walkthrough sheet.

Why & When You Should Inspect Your Vehicle’s Cabin Air Filter

Remember Kyle? The previous owner of his car clearly never inspected or replaced its cabin air filter, and miles of buildup and some errant insulation clogged the filter, resulting in a toasted blower motor.

But beyond the impending replacement motor costs, that clogged filter meant the vehicle’s cabin could’ve been filled with all sort so gnarly particulates—airborne stuff that could ultimately end up in passengers’ lungs and eyes. So while we’re bummed Kyle had to replace his blower motor, the silver lining is that he caught the issue before it could’ve potentially impacted his health.

Here’s a new/old comparison of cabin air filters from our Nissan. The old one had less than 20,000 miles on it. (Image/OnAllCylinders – Paul Sakalas)

Many filter manufacturers spec out a service interval of around 20,000 to 30,000 miles. But again, your specific car, truck, or SUV manufacturer may have different intervals, so check your owner’s manual.

Your driving environment is a factor too. If you’re often driving off-road, or in generally dusty conditions, then you may want a significantly shorter interval. (It’s also something to think about if you’re driving where air quality is impacted by wildfires.)

And it’s worth noting that there’s no real downside to changing your cabin air filter element more often. They’re relatively cheap for a lot of applications and, if it’s easy to do, then it’s not unreasonable to service your cabin air filter with every few oil change cycles (or before/after a long road trip).

4 Signs of a Bad or Clogged Cabin Air Filter

So, outside of removing the cabin air filter for a visual inspection (which can be a bit of a hassle), how can you tell if your cabin air filter element is clogged or needs to be replaced?

There are a few things you can look out for.

1. Less Air Movement

The first relates to Kyle’s story. Be aware of the force/volume of air moving through your vehicle’s HVAC system. If you notice your climate control fan’s not moving air like it once did, then you should check the cabin air filter. Air not getting hot or cold enough can also be a symptom of a clogged cabin air filter element. Just like a clogged engine air filter, a loss of performance can signal a problem with airflow.

2. Blower Motor Noise

On a similar note, if your blower motor starts to sound different, like it’s straining, whining, or whistling, then it’s probably a good idea to examine your cabin air filter as step one in the troubleshooting process.

There’s plenty of stuff crammed in the folds of this air filter—but this is still relatively tame. We’ve seen twigs, dead butterflies, seeds, tree bark…we could go on, but trust us, you don’t want us to. (Image/OnAllCylinders – Paul Sakalas)

3. Smell

For starters, a clogged air filter hinders vehicle ventilation, which means smells may linger longer (say that five times fast!) in the passenger compartment. Also, since the blower motor may not move enough air to dissipate those smells quickly, if you’re noticing that odors tend to stick around, you may want to check your cabin air filter.

Additionally, a dirty air filter will start giving off its own funk. Accumulated dirt, dust, leaves, twigs, and other debris can build up to create a mini compost pile in the filter. Gross, but true. Got a woodsy smell in your car? Check the filter.

4. Visible Particles

Finally, and you can file this under the “well…duh” category, if your climate control system starts spitting crud out of the vents, then yeah, check the filter. Sometimes a filter element can tear or get so packed with debris, that gunk will start making its way through the climate control system’s air passages, on its way to your clean, white shirt.

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Got any cabin air filter install tips?

Better yet, what was the weirdest thing you’ve ever found in a cabin air filter?

Let us know in the comments below!

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One Comment

  1. Liked article on cabin air filter

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