Ref. Sticking vent selector heater controls on 2006 ZX5.Remove drivers under dash panel,loosen hood cable nut and slide off, unclip data connector and set panel aside.Remove 4 screws from selector control ,cables attached, and let hang down. Unhook the black selector gate and feel the action of both front and rear flaps.The main culprit is the flap closest to the radio so as you move that flap you should feel the sticking or stuck condition at both of its far end positions.A deformed internal flap seal causes this jamming effect, so here follows my humble solution, that involves adjustable end stops.I used a 1/16" aluminum strip 3" long and bent up one end about 1/8" at 90 degrees and mounted it on the heater box with short self-tappers against the link of that flap to provide a forward stop.This stop should be carefully positioned so as not to allow the flap to drop into its sticky resting place.If you are close the aluminum is easy to bent so as to get a finer adjustment.The next step is to remove the radio surround panel,disconnect cigar lighter,remove the radio, pull two cables and set unit aside.Drill a hole in the heater box and install adjusting bolt bracket as shown in the photo. It is important to adjust these end stops as minimally as possible or the mechanism will bind. After the two stops are mounted a final check before reassembly is to install the black selector gate back in position and work "by hand" the mechanism through its full motion to confirm that no stickiness occurs in either of its end positions and that it transitions smoothly through its various modes.Although the flap is not technically as the designer intended, my air flow is normal and the cable controls work properly. The cost of materials is negligible and the labour maybe two hours work .The Ford car company does not need any more of our hard earned money so I hope this helps some other physically challenged heater boxes. The cost of materials was negligible and took maybe 2 hours, with a low difficulty scale.