Had a belt burn up in my 1994 F150. Bought the replacement and before putting it on noticed the alternator will not spin. From the looks of it, it's the stock alternator and the truck has over 150,000 miles on it. I don't want to put the new belt on only to burn it up as well. A non-turning alternator means it's junk, right?

 

The Cliff notes version -> Yep.

The longer version -> the alternator should spin freely. Suggest it's time to get a rebuilt, or to rebuild it yourself - bearings, brushes, etc. Given your question, recommend going the "already rebuilt" route.

 

Got it. Thanks.