I have what sounds like a cricket or something under my dash, I suspect it is the temp control door, it works fine but does make an odd clicking from time to time, think mine is on the passenger side.

 

that's what I had! at start up. for YEARS. I never bothered w/the dealer because they would have charged me $200 and written "could not reproduce"..

Mine was the mode door. the passenger blend door looks like a pita. (driver doesn't look too bad)

If you want, you could set the driver to cold, passenger to hot, then vice versa and make sure both are working as they should.