Rattling sound when the heater is on low

So the last couple of days I've noticed this rattling sound coming from the air vents. It only occurs when I have my heater on low. If I crank it up the noise goes away. Does anyone know what may be causing this noise? It's getting really annoying. Thanks in advance.

 

It's a rattling sound. I haven't had time to call the dealership and was worried they would charge me an arm and a leg just to check it out but if there's a TSB... whoo-hoo!

Thanks!

 

My o5 Taco does the same thing hasn't got worse. I figure the fan bearings are getting a little wore, might need to be looking for a new fan motor to change it out. Cold weather will bring the noise louder than warm weather.

 

Thanks brotha! It just get's a little annoying after a while, ya know. So lately I've just turned up the volume to my radio.