In my 2006 Explorer, when I try to turn the blower fan up, I get a humming/vibrating sound, and very little air movement. If I turn the fan on higher, the humming/vibrating gets louder and I get slightly more air movement. This happens with A/C on or off, set to any temp., and any direction (feet, console vents, defroster, etc.) I'm wondering if the fan or ducting somehow got blocked (can you say mouse nest??) Where/how should I check this? Where is the blower motor located and how can I get to it "easily"? Same with any ducting.

This started overnight ... it was working fine yesterday, today it's not.

Any help at all would be GREAT!! Thanks in advance.