only my air direction servo was buzzing ( no selection of direction except face vent) . I was abled to get to the 3rd screw for the vent control direction servo using a mini ratchet from crafstmen i left most of the car intact, bent the servo bracket back to aid installation and removal. im not saying its a better way than a full strip out, i just thought it suited me.
upon dissassembly of servo i found the yoke on the motor shaft was not driving the worm screw because it had slipped back, so i moved it up the shaft a bit with sharp sidecutters supporting the yoke (motor hanging from yoke by side cutters) and tapped gently on the motor shaft to move the yoke about 0.060" until it engaged with the plastic worm screw. the yoke came loose once, so i slid it off the shaft, squashed it a smidge so the hole closed up marginally, and knocked it back on the shaft , it was now very tight, i also used loctite 609 as a lubricator on the shaft... its designed for drive applications and sets very strong. tested out and working fine, thanks to all the adventurists that first took the servo apart to discover its fixable.