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.
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.
Most likely one of your pulleys/accessories has a bearing going out and seizes intermittently causing it to fly.
The belt tensioner is probably bad.
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.
because they are cheap
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.
Assuming the tensioner is keeping the belt tight, you need to make sure all of the pulleys are still in a straight line. If a bearing has failed in a pulley the puley will "lean" causing the belt to run off the edge.
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.