99 Bravada air recirculation not working

Hello, we have a 99 bravada and the recirculation button does not seem to be working anymore, the light comes on when the button is pushed, just no increase in air. It used to increase the fan speed and really blow the air but now it does not do anything. A while ago you could hear a sucking sound when any type of air was on – I have not heard this for a while now(this may be another problem altogether). After reading some of the other posts the only thing I found similar was the blend door problems (of course they were only blowing hot air when cold air was needed). What should be checked or taken apart to fix this? :confused: Does anyone have pics of the procedure?

There's a door, like the blend door, under the glovebox that opens to recirculate the interior air. It's operated by engine vacuum so you might check for a cracked or broken vacuum line.