2001 Buick Century vent control problem AC blows out the lo

The ac blows mostly from down below where heat usually comes out and changing the control does not divert the air to the vents nor does it change the flow to defrost or any other setting. The control does turn on the max for the ac but the flow does not change to the vents where I need it to keep me cool now that summer is here. Ac is cold so the problem is the vent control. Underneath the dash I noticed a plastic arm that I think may be the diverter but I could not move it by hand. I am tempted to start taking things apart but I do not want to waste tme and am liooking for a common solution thank you.