I found this thread from our forum... https://www.ford-trucks.com/forums/7...tensioner.html

it should be helpful. Especially the part about off-idle and a suspected alternator, and removing the belt and spinning the all the pulleys by hand, and how one of the posts specifically mentioned when they spun the tensioner by hand they heard an odd sound...

The Bronco/F250 manual spells it out it just takes more time to read that.
1996 Bronco/F-Series Workshop Manual

..." 3. If any of the accessories are damaged, or have a worn or damaged bearing or internal torsional resistance above normal for any reason. All of the accessories should be rotatable by hand in the unloaded condition. If any are not, the accessories should be inspected.