Getting a loud ticking sound only when the heater knob is turned past half way mark

I have a 2006 Prerunner extra cab, 70k miles.

The weirdest thing happened today. I started my truck as always and this loud ticking sound seemed to be coming from the glove box. I thought maybe something got caught. I turned the car off and back on with nothing changed.

The loud ticking sound continued until I turned off my heater. I then realized that if the dial is turned to AC the sound is gone. I turn the dial to heat and not until Im at the half way mark between warm and hot does the ticking sound start back up. As a temporary fix Im just not turning my heater on full blast.

The ticking is so loud that when I put my hand against the center console I can actually feel the vibrations from the ticking.

What could this be? and how do I fix it!????

 

The blower motors are notorious for this! Either lube/ grease or replace!!!!! This might be it. Although no mention of the A/C to heat control doing anything...

http://www.tacomaworld.com/forum/2nd-gen-tacomas/28355-blower-motor-squeek-chirp-low-fix.html

 

Pull your cabin air filter. Probably a leaf or somthing hitting the fan blade

 

Yeah it has nothing to do with the setting of the blower, just the heat/ac dial.

I hear the same clicking sound when the knob is turned to heat regardless if I have the blower on low or high.

 

I had a similar issue with my old corolla... turns out I had a mouse in the blower.

I had talked to a buddy of mine who works for Toyota about my issue - I didn't believe him when told me that mice were notorious for getting in there...

30 mins later I sent him a pic of the mouse with a caption of "I hate it when you're right"