Alternator - OEM or Aftermarket?

[proslambanomenos]

Yes, thanks for the reminder--the pulley was the proper size and groove count. I can imagine depending on what vehicle the reman was pulled from, the pulley may be different. In my case this was not an issue.

 

[proslambanomenos]

Another follow-up 10 months later--the reman oreilly alternator's voltage regulator (built-in) was dying. Interestingly enough, it passed the bench test. But I run a 12v fridge and a mobile ham radio, both which are sensitive to voltage drops and which automatically shutoff if the voltage gets too low. The ham radio would just not run sometimes as a result. The lifetime warranty came in handy as it didn't cost me anything. The swapped unit seems to be working just fine.

 

[bbyer]

normal bench tests do not work

Your comment regarding the bench test make sense.

As a rule, normal bench tests do not indicate regulator failure in that they will show the regulator as OK when it is not. This is because the regulator listens for some sort of Pulse Width Modulated signal from the engine computer rather than a conventional voltage signal from the battery and a bench test with conventional alternator test equipment is not designed to test the PWM signals.

There is also a sort of fail safe circuit feature within the regulator that defaults to about 13.3 volts, hence I suspect the bench test showed a constant 13.3 volt output. If so, that is the indication of regulator failure, and yes, the alternator itself is most likely still OK.