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Cabin A/C air filter replacement a necessity or a nice to have?

I know the cabin or A/C air filter is to filter out pollutants, etc. like the ones in home A/C so you have more comfortable & cleaner air into the car.

But is it really necessary to have & replace or just a nice convenience (and thus extra hassle to maintain) in modern cars? I believe old cars 2 decades or more back didn’t have these right?

Just asking this because

(1) I don’t care that much about really clean air coming into car, and more importantly

(2) I just replaced the cabin air filter in my Suzuki Forenza. I didn’t know it had one until I did some research. Manual didn’t really point it out, and the dealer & mechanics never mentioned it whenever I brought in for service. So all this time, I think I’ve been using the original filter for 7 years (60k miles), or if not then at least half that (assuming dealership did their part to replace the filter at the right time for 30k or other interval service). The original filter mentions to inspect & replace as needed and using a dirty one can damage the blower or something like that.

So what’s the worst that can happen if you just keep using same old cabin air filter and never replace it? Will it kill your heating & A/C system or parts of it? Or just really dirty air over time?

You should replace it eventually, the one on the Prius is supposed to be checked at 30K and cleaned if needed then replaced at the 60k service if i remember correctly. A dirt devil or similar hand vac might clean enough dirt out of the filter but aftermarket filters are available for most cars at a fairly reasonable price. The owners manual for my mom’s 2010 prius shows you not only where to find the filter but the method for cleaning it if needed. Or replacing it depending on how dirty it gets. Suzuki might suggest a different interval.

As the filter begins to get plugged up you will notice less and less airflow into the cabin. I’ve seen filters so dirty that even with the fan on high you could barely feel the air coming out of the vents. Do this long enough and you stand a chance of burning out the fan motor, since it’s working so hard to push air through a plugged filter.

Thanks for the comments, good to know.

Guess I should be safe then I think. Air flow seems to be same or only slightly worse over time (with the old filter in). I’ve never went above fan speed 2 and it’s always worked fine for me to heat the car or cool the car. The filter I just replaced looked dirty with some small pine tree, etc. debris in it, but it didn’t look super dirty with dust falling off it when I took it out.

I can tell you from experience what will happen eventually. Our 97 Accord didn’t even come with a cabin air filter, not sure any car did back then. Eventually dust, buts of pine needles and leaves etc got into the vent system and clogged up the evaporator coil. The debris also clogged up the AC drain and blowing compressed air up the drain tube was only a temporary fix for that, it would be clogged up the next day.

Now if you are familiar with the 97 Accord, there is only one thing you can remove from the HVAC system without evacuating the AC system and that is the blower motor. They also put a hard bend in the vent between the blower and the evaporator so you can’t go through the blower motor housing to clean out the evaporator like I did on my 97 Nissan when that happened to it.

The evaporator housing is a clamshell with hidden clips and screws on the back, so the evaporator has to be removed for cleaning. What a mess. But compared to a Toyota, the Honda is a piece of cake. The whole dashboard has to be removed in a Toyota, right down to the firewall.

But the industry is making a killing on these filters. They are way overpriced. They aren’t even close to HEPA grade, but they are costlier than the 20" x30" HEPA grade filters that I use in my house HVAC. They shouldn’t cost over $2-3, but yet they run over $20 in most cases, $18 at Walmart.

And then there is the installation charge. If you let a dealer replace it, it can cost upwards of $50. Since it is done in conjunction with other services, it should not cost anywhere near that much. I could see that charge if it was a standalone service because of the cost of moving the car around, getting the filter from stock and doing the paper work. I think its the dealer’s way of punishing people who are too lazy to open their glove box, read the owners manual and replace the filter themselves.

BTW, I put a piece of mesh filter over the intake to the vent system in the Accord. I will have to pull the cowling to replace it when needed, but that is a whole lot easier than pulling the evaporator.

As mentioned, the dirtier a filter gets the less air is able to pass thru the filter. If the system had a high static fan where it could overcome this restriction it wouldn’t be a problem. But auto vent systems use a cheap squirrel type fans which don’t produce high static pressure to overcome a dirty filter.

And you cannot burn a fan motor up from the lack of airflow. If the fan isn’t moving any air, the motor isn’t doing any work. This can be demonstrated by blocking the hose of a vacuum cleaner. When the hose is blocked and no air enters the fan, the motor speeds up because it’s not pumping any air.


I just shake and tap out all the junk in the filter and reinstall it.

The filters aren’t all that expensive when purchased at auto parts stores in my opinion. I replace these filters at regular intervals just as I do the furnace filters in my house. I rather enjoy breathing cleaner air. I used to wonder years ago why filters weren’t a part of the HVAC systems in cars. Now they are. Even at my advanced age, I like to keep up with the improvements over time.

Seems sota pointless to filter vent air, yet have windows that roll down!

At any rate, the cabin is hardly a pressure vessel…what purpose does the filter serve, other than revenue enhancment?

My car came with the cabin air filter box, but they didn’t start including the filters until the following year.

I’ve driven for 45+ years without a cabin filter. Is it a good thing? Sure. Is it necessary? No. But of you have one, it’d be a good idea to either toss it or replace it so it doesn’t become a bacterial breeding ground.

The purpose to me is to keep junk out of the vent system. I discovered (14 years late, it’s not mentioned in the owners manual, I happened to find it when looking up an engine air filter) that my '96 had a filter, but never had one installed. When I opened the filter ‘door’, all kind of junk fell out - leaves, pine needles, dirt, etc. And that was also the front of the a/c evaporator, so it was plugged up to some extent. Had I known it could use a filter, and had put one in there from day one, all that stuff wouldn’t have been in my evaporator.

As has been said, all of us lived for many years (perhaps many decades) w/o a cabin air filter.
However, that does not mean that this feature is without value.
For somebody like me, who suffers from seasonal allergies & asthma, a cabin air filter is very valuable IF it is changed on the correct schedule.

If you don’t want to change it on schedule, then it would be far better to simply remove the filter, rather than attempt to run the HVAC system with a restricted flow from a clogged filter. Aside from potentially damaging the HVAC fan, a restricted air flow can lead to an inability to quickly defog the windshield, and that is a definite safety hazard.

As to the folks who think that something is not necessary simply because it didn’t always exist, my response is…So…you don’t think it is important to have running water, flush toilets, a refrigerator, and central heating & A/C in your house?

Time marches on and standards of living change over the years. What was once considered to be unusual or a luxury later becomes an expected part of life, due to it being something that makes life…easier…more comfortable…healthier…or just plain more enjoyable.

I replace ours about every 3 months. And they are dirty when I replace them. Thinking of doing it every 2 months.

You should either keep changing the filter periodically…or remove the filter altogether. As MB pointed out…we ran for years without one. I like the idea of breathing cleaner air.

I believe Tester is wrong about the effect of a blocked filter. The noise he hears on a vacuum is the motor straining. The blades slow down because there is a partial vacuum on the intake side of the fan, and they have to do more work. Since they do more work, and run slower, there is more electrical current through the motor, which will cause it to burn out sooner. So filters need changed. I think that the Merv rating of these car filters is all over the map. The one on my Toyota Avalon only takes out big chunks (like geese that accidentally got drawn into the intake). After 30,000 miles you can still see through it. Obviously, other people need to do it more often.
Probably depends on where you live, too.

It all depends where you live. I replaced the one on our Toyoa after 2 yearsa nd there was hardly any dirt on it. The car is nearly always inside.

If you never replace it, and live in a dusty or windy area, it wll plug solidly and you won’t get any air through. If you take it out and never replace it, you will have a “pre-filter” car, and your interior will get more dusty.

@melott - no, the motor speeds up, it’s doing no work (moving no air), so it spins faster.

our car has filter accessed under windshield wiper panel. removing 1 wiper arm is annoying. you would think car maker would notch the plastic panel. our filter was black. very dirty.

Either replace it or toss it. These filters are quite profitable for the dealer. My Toyota dealer wanted $30 parts and $30 labor to replace mine at 15000 miles even though The free for 2 years Toyotacare pays the dealer to remove and clean the cabin filter at that time. I bought one at the parts store for $7.

@melott: No, restricting air inlet to a squirrell cage reduces effort. Fitness center ergs and stationary bikes have a means of blocking airflow to the fan: more restriction = easier (from personal experience!)

On my Civic, after 50K on the original filter, I just ripped filter element from the plastic frame and siliconed in a piece of window screen.