Noticed that a squeek I've been chasing may be the AC belt. Hit it with some belt dressing and the squeek went away while the engine was running. I take it I need to take the main drive belt off, but then do I have to yank on the tensioner to get the AC belt on and off?

 

I believe I got rid of the squeek that has haunted me for years. Like I thought, I had to loosen the serpentine belt to get the AC belt around it and to put a new one on. Now.... No squeeks! Proof that idler pulleys are not the cause of all squeeks.