Question A/C Cold Air Blows Out One Vent

[TiffLeigh3]

I have a 2001 Toyota Highlander. I used to have pretty good air that would usually get really cold (which is great given the fact that I live in hot, humid GA) - but just recently when I turned my A/C on, I kept feeling like the air never really got cold even though it was on the coldest setting and the A/C button was on. Then I somehow discovered that there was in fact cold air coming out - GOOD COLD AIR - it just only comes out the LEFT PASSENGER SIDE VENT. All the other 3 vents blows lukewarm to slightly cold air, while the left passenger vent appears to be blowing ALL the cold. What do I need to do - why is this happening?? Someone told me it might be a "mixing door" or "mixing switch" but I don't know what that is, nor do I have a diagram of it. Any help would be appreciated!
Thanks!

[LifeTech]

Mixing door is one area to look at...but IF yu have a Cabin filter and it is completely clogged with soot and dirt...yu get a similar issue. They should be changed out every 15K or 1 year. Located behind the Pass. Glove box.

Check if yu have a cabin filter.. my 06 HL does and my 01 Avalon does too. My Avalon had a similar issue and replacing it fixed the air flow problem.

It is possible that yu don't have a cabin filter... then yu will need to focus on the air mixer. Alot of tear down to the lower dash will be needed.

Good luck

LT