The air flow with the fan on or off was slow at best and with the fan, well the fan was 'hunting' to pull air. So I bought a new filter from NAPA auto parts. So simple I thought I would capture it on JPEG....
You have to remove two screws to uncover the area to work in, simple with a cross head driver and they are not too tight. Press latch and pull top catch to lower end of filter cover, remove completely. Rock old filter out.... I was surprised how plugged the old filter was (second photo) !
Clean any debris in chamber, use your finger with latex glove or non-alergenic type. Follow arrow on filter and rock carefully into chamber slot as not to tear sponge gasket. You will have to position filter as in last photo to get it past floor pan angle.
Now my air flow is strong with no pulsing (hunting) to pull air in. Smells better too!
This is for the 2004 and older S40, other Volvos may be somewhat different in size, location and difficulty.... My S40 time was about 15 minutes.

poikaa

 

I appreciate this thread I just bought my s40 last week and the ac was starved for air and now I know why, thanks again man. Man I love this forum.