Hey, I have a 1998 Tacoma V6. When i turn the fan control knob all the way up the air seems to only blow through the defrost vents and the driver side(not alot of air) vent. Thats it, when i try to switch it to the floor or any other mode it clicks but nothing happens. The heat works fine. I've heard it could possibly be a vacuum leak?? Thanks

 

Dirt or mouse nest in the duct work

Which could be keeping the doors from moving like they should

 

The 98 Taco is cable not vac, objects can fall down the defrost and block/jam the blend door flap, there are little gears in the knob causing the clicking as they can't move the cable, also the cable itself could have failed or got kinked, I think the blend door is behind the stereo unfortunately but you may be able to access it buy removing the lower dash.

 

will check under the dash then. Thanks for your replies.