My car is over two years old (purchased 10/99) so I decided to check and then replace the cabin (A/C) filter. I was really surprised how dirty it was.. it does a great job of filtering and was quite nasty with dirt and stuff.

I suggest you consider replacing it after a couple of years. Good price from sponsor http://www.handa-accessories.com/s2000.html .

 

Ah yes, I did that about a year ago.

https://www.s2ki.com/forums/showthread.php?...t=heater+filter

Pictures are gone to the links but I still have them in my hardrive, I will post it again if anyone needs to see.
I think if you are a daily driver, you may need to replace annually or even sooner.

This is something people may overlook maintaining the car so make sure you take a peek inside to see what condition the filter is in.

 

The Normal Maintenance Schedule calls for replacement at 30,000mi or 2yrs.

 

...and as usual, the recommended service interval is for people who don't drive their cars.

 

I replaced mine about a month ago (I have over 50K miles) and it was completely dirty. After putting the new cabin filter in, the heater and A/C works much better. Like Chris said I couldn't believe how dirty it was...OMG!!

It takes all of 5 minutes to replace the filter. It is a must do.