just wondering if anyone else has had a problem with alternators from Advance Auto parts? This is the second one that went on my Rodeo within a year, causing the Battery to cook. voltage ran around from 14.0 to 14.4 on the way home today. could it be something else causing the volt reg. to go?


1991 Isuzu Rodeo
V6 4x4
137,000+ miles.

Alternator output voltage is supposed to be around 14V while charging.

Going to say the same thing...14 volts isn't that high and your gauage may not be completely accurate. Now I had an alternator on my trooper that went bad and was charging in the low 20's...it blew out every light on the truck (driving at night)... got lucky though the computer was fine.

Your battery is fine between 13 and 15 , thats average charging rate.Once it gets higher than 15 , then something is not regulating it properly.Either the alt is going or the voltage regulator.Also , if the alt says its between 14 and 15 and its frying the battery , then your guage isn't working , or something else is contributing to the distruction.Possibly a short somewhere in the charging system?

14V actually coresponds to something called TVG (Temperature Voltage Gassing) or Gassing Voltage. TVG is basically the voltage at which gassing occurs but the heat produced from charging isn't excessive enough to cause plate damage. Gassing mixes or circulates the electrolyte which increases battery by increasing the specific gravity at the top of the battery. Once you get above TVG for extended periods the active material on the plate can start to shed producing internal shorts and reduced capacity.

guess I should have also mentioned that along with the standard dash guage, I also have a stereo that monitors and shows voltage, I have confirmed that the stereo shows very accuratly what the volts are. Also, I did notice while cleaning the battery posts (just in case) that the possitive had a sort of dark coating to it, the neg. was clean. but one side of the battery was bulged out some. A friend of mine suggested that maybe the battery itself may be to blame???? and if i am not mistaken, the voltage reg. is built right into the alternator on this application. Thank you all for the quick replies!!!!

You are correct on that point. But as stated above, 14.4V is within the normal range.

If your battery is bulging , I'd say thats the problem.There should be no signs of deformity on a battery.Any damage to a battery can cause problems.A place that can check it for you I'm sure will verify that its not a good thing and probably recommend a new battery.If its bulging , it could be on its way to eventualy blowing up on you , and thats not something you want to happen under the hood , one big mess.