Just because an alternator regulator has a thermistor in it does not mean it will always protect your alternator from cooking itself. This alternator was charging a large bank of flooded batteries, almost 900Ah. It got so hot that it had cooked the stator as well as melting the seal out of the front bearing. An external regulator with alternator temp protection could have saved this customer from an expensive repair.


If you want to protect an alternator, to make it through the warranty period, reducing regulation voltage can work okay, but it did not here.. If you actually want to charge batteries, used in deep cycling applications, and do so in a healthy manner, alternators with internal thermistor regulation are really quite a poor choice.


In a marine application, the regulator in these alternators is only about one thing, protecting the alternator from a melt down. Course as we can see that was not the case for this thermistor compensated alternator. Automotive alternators are not about charging performance nor do they care about your batteries. Slap it in a car, where the batteries are always full, and you're good to go. Put it in a boat with deeply cycled banks and they really perform quite horribly.