The fan switch has tiny plastic bits stopping the rollers from going too far and jamming. Obviously, they eventually fail.

I object to paying for a new switch. They come apart with a bit of persuasion, and can be pop-riveted back together. I drilled 1/16 holes through the whole switch, at exactly the right place, and pushed 1/16 cotter pins through to stop the rollers from over-centering and jamming the switch. The result is much stronger than new. I only wish that I had done all the switch positions the first time I had it apart.

And, yes, the dash has to come apart a little bit. Center vents out, exposes the screws, centre plastic bit out, tiny wood strip out (oh so carefully), reach down to unhook the A/C clips, pull out A/C panel, then the switch comes out.