AC/Heat Rattling/Vibration sound

[puertorock]

Car: 2007 4dr Yaris

Hello all new to the forum, but am in need of assistance. Before I wrote this post I tried to do a search to try and resolve my issue, but came up with only bits and pieces of what I needed. My issue come from my AC unit in the car I believe, when I turn the AC/heat to the 4 position it make a very loud rattling/vibrating sound very annoying. It Cools/Heats and blows very well just an annoying sound. The lower down the numbers I go the lower and less annoying the sound gets. When I get to position 1 there is no sound at all.
After doing multiple google searches, I found 1 something can be stuck in the air ducts. Or 2 the AC/heat Fan can could be dirty or have significant particles.

My questions to my fellow Yaris enthusiasts are:
Has anyone had this issue?
Where is the AC/heat Fan located on 2007 Yaris? (I feel stupid) (A picture would help)
What is the best way to clean the air ducts?
And any tips on pulling the Fan out would be helpful.

Thanks Guys for any help!