Interior fan blower weak airflow

[Orinoco Blue S60]

Whilst sorting various niggles with the s60, I've noticed the interior fan whilst spinning at full tilt moves very little air, it's a tiny breeze even in max speed.

Any ideas of common cause? It's the same whether using ac or not, on recirc or not, just not very strong. Like it's escaping somewhere or not pulling enough air in in the first place...?

[stuart bowes]

clean or replace the cabin filter? (I changed mine to the carbon filter thinking it was something of an upgrade but it slowed the airflow massively so I went back to the normal one)

blocked external intakes (on the scuttle panel I think) full of leaves or something

flap mechanism working correctly and not half blowing out down by your feet or up at the window?

I believe there is a calibration thing in VIDA which can make a difference in certain circumstances

the fans and/or regulators can die, bit of a pain in the arse to change but doable

[XC70Bob]

Also check that the panel were the filer is inserted in is fixed back correctly with the 4 screws, as the fan blows through the filter so if the panel is poorly fitted air will escape under the dash.

[xeyone]

After all steps above, check the blower resistor.