Air vents

On my 1997 tahoe 5.7L, the floor vents will vent air even though the "selector Knob" is turned to the console vents. (the vents by the radio, instrument cluster, and so on) What is the problem?

Also, it is time to replace the shocks, any suggestions about any brand to replace with. I do very mild off-roading about once every month, and rest is city driving.

One more question, what exactly does evacuating the a/c do to the system and how often are you suppose to do this. Mine is starting to blow air that isn't exactly cold.

Rancho shocks are good. There are many shock companies that are good though.
You should never need to evacuate your system unless you have a break in the system. Have them check your system to see how much 134 is in it. If need be, have them add until the proper amount is in.

You may have a slow leak that is so slow that you don't need to even repair it. If it goes 2 years between recharging, then it's fine. No worries.

on my 98 2 door i have the same problem with the air vents coming out of the floor when the knob is on console any suggestions?