Today a new noise began emanating from under the hood. Thought maybe some grit or gravel from snowplowing had made its way under the hood, but it continually got louder and more consistantly present today. By the time I got home, it was enough to cause me to pop the hood and investigate.

Its 100% coming from the serpentine belt, near the left (of two dual) alternators, possibly from the tensioner mounted below...but...how to tell which one???

How about a can of WD-40 with straw engaged, starting with squirting the tensioner? Then...if not the tensioner, a small burst behind the pulley on the alternator?

What say ye for my test methods to ISOLATE THE SQUEAKER?