I changed out my FSR to a new.
I was getting variable AC volume of air.

I can hit max blower and it seems to straighten out.
And blow normal flow.

I am NOT hearing the blower RPM decrease.
It seems as if the ducting is becoming blocked.
The air flow volume decreases without the fan RPM dropping.

After about 30 or 40 minutes the flow seems to
decrease to a trickle.
And the process starts over.

Any thoughts on where to start?

__________________
2003 4.6is X5
2003 525it
2003 E53 X5 Standard shift