well i got a servo motor going bad think i might document a DIY on this if thats what the problem is..........sounds like yours is also

 

yeah man its the weirdest *****....it was buzzing on and off the whole time i drove at first, then constantly for about 20s when i first started it, now its doing a combination of the two.

if you could do a DIY that'd be dope. Idk if its the motor going bad or just needs grease, it's seen 7 years of heavy AC use in summers and heat use in the winters up here in New England.

 

Servo motors on the blower box, trying adjusting where the air comes out...
i.e dash vents, floor, defrost. If the noise happens then thats the servo motor you need to replace. if not try the hot cold, then listen for the same noise. also try the recirc. button, and again listne for the noise. once you have diagnosed the problem order the new servo motor and install.
The motors are located behind your glove box.

good luck.