We rebuilt alternators in college, I still to this day don't understand why its not more common, parts are cheap. I mean I'm not in the business, I'm not sure the failure time/rate of the windings themselves, but everything else is cheap and replaceable. I should pick up a test bench if I see one on an auction.

 

Labor rates.

It takes time to rebuild it, and looking at comparative costs, it's actually cheaper to REPLACE it, than rebuild it. (if you are paying someone else to do it, at any rate)

As for rebuilt vs. rebuilding..... No, ya don't really know what all they do to the reman units.... but, they DO come with a warranty.... The better the warranty, generally implies a higher quality rebuild. If they only offer less than one year, look for another brand.... That isn't a hard and fast rule though.... I have had parts with 'lifetime' warranty, that I was replacing every three to four months, due to failures.....

 

Maybe I’ll land in the middle. I have the old unit. Seems like a pain to send it back to rock auto for the core. Maybe I’ll rebuild it and keep it as a spare.

For what it’s worth, I have a pickup with electric fans and I think I may be having an issue where long idles are draining the battery. It seems the alternator current drops off exponentially at less than 1000 rpm.

 

Could put a smaller pulley on the alternator to spin it faster.... I would expect that will shorten its life though... How much? Don't know.....

 

Definitely weight the cost, sometimes the core refund is less then shipping. There's no money in sending it back. Rock auto does give a shipping discount if you purchase it through them and you have option to have the shipping payed by the core return money I believe, so there's no upfront cost.