self ajusting idler wheel strong spring inside housing
It provides the proper tension on the serpentine drive belt.
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 )
Your Explorer has a serpentine belt tensioner which keeps the proper tension on the serpentine belt unless the tensioner has failed.
Check to make sure that the serpentine belt is ok, and that the ac clutch is working properly. Make sure that the serpentine belt has the proper tension.
It provides the proper tension on the serpentine belt so as it is not too tight or too loose.
Put the proper size wrench or socket on the pulley of the tensioner.Pull the wrench counter clockwise to release the tension on the belt.
A serpentine belt on an engine is held in place by a pulley that maintains the proper tension on the belt. This pulley can be pulled up to release the tension on the belt. Do not pull the pulley out, but gently up or you'll risk damaging it.
Possible belt stretch or an idler not applying proper tension for some reason.
Should automatically supply the proper tension for the serpentine belt - if not could be defective and require replacement
You have a mechanic check for proper belt tension. Trust me, in the long run this is the smartest, safest and CHEAPEST way to solve the problem.
Most cars now have a serpentine belt that drive the alternator, water pump, power steering unit, etc. The belt tension pulley is a spring loaded pulley that keeps the proper tension on all these units. It can be moved to release the tension in order to remove the belt.
You cannot tighten the belt. It has a tensioner that holds the proper tension. If the belt is loose then either the belt is worn out or the tensioner has failed.