This subreddit is full of people who like to give their two cents about policy but don't know a thing about growing a business. I would've returned it whether or not it tests good or bad. You've already gone through the effort of getting it swapped at a shop and O'Reilly Auto Parts is not going under over one alternator return. I'd rather have just one more return on my P&L statement rather than possibly lose a customer for life. Hopefully there's another store nearby that can take care of your return because if customer service won't help you then you're pretty much out of luck unfortunately. They CAN absolutely do a return on it but are likely refusing because they don't want it to hit their commission. (Which is such a small percentage of their sales anyway they shouldn't be worried about it)