HVAC air distribution control diagram

My '03 Avalon XL won't put any ventilation to the floor in either full nor part settings.

My dealer told me it was something to do with the "timing" of the electric heat/AC control not opening the damper doors on the correct time.

I understood none of this, but the service writer was too busy, I guess, to want to write up an estimate or take me to any shop manual on the premesis to show ne what he was talking about.

He did say it would require 3-4 hours of taking apart the dash just to go find out what the problem is!

I can buy the factory manuals for less, but this will take a while.

Can anybody fill me in on what's going on with this? Anyone able to scan pictures of the HVAC manual for at least an illustration of the system?

Thanks