Usually when I used to press the recirc button on the automatic climate control, 99 SLE 3.8 K, the sound would change indicating that something switch from letting outside air in to recirculating inside air. Now when it'* pressed no change. How can I check what is going on? what is supposed to be moving or actuating?

Anyone?

Try a system relearn.
For non vacuum operated systems (electronic) the module needs to learn the full open and full close positions of the doors.
AC reset
Turn the system on full cold Max AC.
Radio OFF.
Turn ignition OFF.
Pull the HVAC (AC) fuse from interior fuse box. Leave out for 1 minute and replace.
Turn key to run/on position....NOT start.
Do not touch any controls. You'll hear the doors (actuators) being opened and closed. The HVAC module is learning the full open and full close positions. Wait until the system is completely done with the learning process. Less than a minute.
Start and test the system.