Is it a clicking sound that starts when you start the ac or car and then stops within about 10 seconds? because if so I got it fixed for about 150$ and it was I think the module inside the air conditioner that had a broken piece and prevented it from changing gears, think of a broken gear so it got stuck and went back and fourth and that caused the clicking sound not everything worked fine on the air conditioner. The car was in a reck so I think that is why it happened on my 2011 Mustang
. Not sure if this is the same problem because it was a clear clicking sound.