2010 1500 Defroster doesn't

[pinenut]

Problem started a year ago: whatever diverts air flow to heater /defrost/mix etc. started clapping LOUD. Dealer fixed. Started doing it again a month or so later. Spell fixed, with a U.
Now entering a Yukon winter, NONE of the positions on the dial works. Fan on full. no significant air flow from defrost. Any ideas?
The best I can say is it doesn't clap anymore.
Thanks

 

[pinenut]

Checked other posts about defrost etc. Everybody else has one or more positions on the switch working. None of 'em work on mine.