I have some used parts that I'm trying to sell - one of them is an alternator from a GMC 6.2L diesel. It's a Delco-Remy alternator, looks farily new. It has one red lead marked 'Bat' - presumably for Battery. The other connector is a plug with two prongs - what is that for?!

I still have the V-belt for it so I could maybe hook it up to a drill somhow and make it spin. How would I measure the output to see if it's working?! I can post a photo if need be. I remember something about Advance Auto testing alternators - do you think they can do it outside of the vehicle?!

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1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K