The belt tensioner is probably bad.
The belt tensioner probably needs to be replaced - about $110 @ PepBoys. Check the alignment of all pulleys. If something isn't aligned properly the belt will keep breaking.
Most likely one of your pulleys/accessories has a bearing going out and seizes intermittently causing it to fly.
If it is a serpentine belt the idler pulley more than likely needs replacing. If it is a drive belt you are adjusting it too tightly.
A serpentine belt has an idler pulley on is to keep it tight at all times. If your serpentine belt is loose, then something is worn out. Its possible the idler pulley is stuck in its bracket so it cannot move or the spring on it is worn out.
belt tensioner is bad or one of your pulleys that the belt rides on is bad or out of alignment.
If your vehicle has a serpentine belt that is used to drive the accessories ( alternator , air conditioning compressor , power steering , etcetera ) the serpentine belt has a spring loaded tensioner that is supposed to keep the proper tension on the belt ( if it is working correctly )
There is a spring loaded tensioner that is supposed to keep the serpentine tight. If it is loose, it needs to be replaced.
it means you need a new belt...plain and simple....lots of people keep driving on their cars when a belt squeaks..and allit does is lead to other problems..... i am no expert, but i think it is the Drive belt that is squeaking
There is no adjustment, they use a belt tensioner to keep it tight. If it is loose it need to be replaced.
Your belt is either to big or just plain worn out.
look at your belt with the engine running (keep your fingers out) the pully on a little arm that bounces is your tensioner.
replace the spring loaded belt tensioner as it's the only thing that will keep the serpentine belt tight.