Thread: Alternators

I have a question regarding with what the volts output is from the display unit inside the car. My alternator was charging at 15.25 volts today and I found it excessively high. Thoughts anyone?????

By the way is an 2005 GXP 5.3..

Originally Posted by Crispy

I have a question regarding with what the volts output is from the display unit inside the car. My alternator was charging at 15.25 volts today and I found it excessively high. Thoughts anyone?????

Mine has topped out at 15.10 volts. That was on a sub zero day in Wisconsin after sitting all weekend. 15.25 is a little high but acceptable if your car was sitting for awhile. The BCM tells the ECM what level to charge the battery at based on ambient temperature and the relative state of charge of the battery. Consider changing your battery out if it is more than a few years old. A sub par battery will torture your alternator and cause it to fail prematurely. My voltage dropped to 10.2v when my alternator failed. It was so hot that I burned my hand when I touched it. I put in a new alternator, battery, and serpentine belt. It's been fine since.

GXP02 the Battery is about a month old. Its a Napa Legend Battery. That is the highest I ever seen the volt meter go yesterday. Normally it would charge over 14... for 5 mins and then go under 14 all the way down to 12.7 and roam around from there to 14ish... I don’t know if this is the norm with these GXPS or not...

Crispy, that sounds normal. if it goes below 12.7 the alt is going.

Mine has experience this lately as well, usually between 14.5 and 15. I has run lower a few days, then back up, then back down. I keep the display on volts on so I can monitor it. Mine is an 08, original alternator with 132k and a red top that is a few years old. Not looking forward to an alternator replacement, read up on it a good amount and the failure rate of the junk out there is very high.

Originally Posted by rottonj

Mine has experience this lately as well, usually between 14.5 and 15. I has run lower a few days, then back up, then back down. I keep the display on volts on so I can monitor it. Mine is an 08, original alternator with 132k and a red top that is a few years old. Not looking forward to an alternator replacement, read up on it a good amount and the failure rate of the junk out there is very high.

My 08 failed last year. Gambled on an rebuilt (supposed to be new) from Amazon and so far has been very good. I keep the volts up on the display also. The highest it has gone is 15.10 the lowest 12.9. For less than half the price of an acdelco it was a good deal. The flucuations are normal. Controlled by the ecm and bcm. I hear of a lot of garbage alternators including remy and rebuilt ac delco. Its a roll of the dice on getting a good one.