That cable opens the "air" door. Otherwise the fan has no intake. To get at the lever it's best to pull the glove box out. Even with it in you can reach up and over the top behind the heater control mounting location and feel the lever. There is a special clip for this lever, different from the other two that holds the cable in place. If the cable is binding, remove it and soak it in WD40 while moving it through the range.
