I've searched all over the internet and cannot find the answer to my problem

I have a 99 Mazda Millenia and the middle air vents will not blow out air. The passenger and driver side air vents work just find and blow out cool air.

The middle vents don't blow out anything. It seemed to stop working once we got the timing belt changed.

Any thoughts or advice would be greatly appreciated!

 

It is probably an issue with the venting system, not related tot he work on the timing belt.
Look a '8' in this picture

This door is directing the air into the various ducts. It may be stuck or broken. Also check the switches or cables at the selector.

 

Do you think this is an easy fix or something I could do myself?