Sorry to resurrect an old thread, but I've just inspected my pollen filter and air system on my Volvo as the heat and aircon was notably less good than it used to be, it would get cold and warm but no real force of air into the cabin like I remember.. and steamy windows in cold weather.
After digging out a bunch of crud from the intakes under the bonnet just under the windscreen wipers I pulled the cabin filter out (passenger footwell behind the glove box) to find this!
It was a real pain to get to (I'm guessing its simply not done on services despite it being on the list) A panel has to be unscrewed right at the top back of the footwell, then the filter housing has 4 torx screws which are a real pain to get to, involves lying half sideways out of the car slightly upside down with a vey short driver (I didn't have one short enough so I had to use some mole grips to grip a torx bit)!
I'm not sure it's EVER been changed after I rinsed it in some warm water, and it's a surprisingly large filter, about ten inches square.
This is the 3rd rinse of hot water with a bit of detergent splashed in.. I will buy a new one but cant for a few days so thought I'd wash it a bit and see how it went.
I think it's safe to say it was blocked up looking at the colour of the water, it was as black as used engine oil!!!
Before:
After: