First, an alternator either works or it doesn’t. No in between, either good or bad. To know you have to test them. Second, most alternators are made off shore so getting a defective one is not that far fetched. If yours tests bad find a starter/alternator shop and have it rebuilt. You will end up with a better product. If your doing an excessive amount of idle time you may have to upgrade your battery and go to a bigger alternator like the commercial guys do. JMO
