Alternator Overcharge?

I was headed home after work today when I heard the alert ding, and looked at the DIC to see "Charging System Failure"

First thought was alternator was dying, so I reach up and switched the DIC to voltage to see it at 15.3, then it almost immediately dropped to normal range. I kept it on voltage the rest of the way home and it was contantly in the normal range, never going above 14.44.

Was the overcharge a fluke? I searched but most results were about low voltage. Anyone else ever encounter this? Is this possibly a sign of impending doom for the alt?

what year is your GP? and you might want to check the voltage regulator plug on the alternator..its the 3-wire plug on the back of it.. make sure its connected. thats the only tip i can think of

Its an 07. I'm going to pull it in the garage and clean up my terminals and check the plugs on the alt. Things have still been ok today, but if anything changes I'll post up.

I had a similar experience with my '04 shortly after purchasing it. It started with the "charging system failure" message appearing on the DIC randomly then after a few weeks progressed to a state where after the message was displayed the car would lose all power while driving (as if you shut off the engine and disconnected the battery) then after being dead for a few minutes the car would suddenly awaken, start and run as if nothing had happened.

I found my fix in a bulletin but that was four years ago and I have not been able to find a copy recently so I'll just go from memory. By performing the following procedure I also eliminated a number of electrical gremlins I was chasing at the time so for anyone else reading this keep that in mind when diagnosing random and or intermittent electrical problems on these cars. The following applies to the 2004 model year but assuming your '07 is probably very similar it is worth a shot.

At the negative battery post, follow the small black wire to the point where it bolts to the body at the frame rail next to the battery (not sure about the older models but on my '04 this is the only ground connection between the battery and the body of the car and when it corrodes it causes a poor ground for every circuit that grounds to the body of the car, the larger negative battery cable bolts to the engine which is insulated from the body by rubber mounts). Remove the bolt and clean the ring terminal and the bolt thoroughly then sand a small circle around the bolt hole to bare metal the same diameter as the ring terminal to increase the area for the ground to contact. Re secure the connection then coat the bolt head/connection and surrounding area with grease to keep the moisture out.


Hope this helps you out, Good Luck!

Was the overcharge a fluke?

Probably not. Most likely a warning sign of the battery going South. Thats how my battery issue started on my '08 GXP. The OE AC Delco battery leaves a lot to be desired if you still have it installed. Not a matter of if it will go bad but when.

I was looking at the battery as I cleaned the terminals and it appears to be the original one. So its pushing 5 years now. Worse comes to worse I can probably throw the battery from the Stealth in there. Its got a higher CCA, and as long as it fits the battery box and isn't too tall then I should be good.

In looking for a replacement battery the problem I had with my GXP was fit and form factor so I had to replace it with another similar AC Delco but the better AC Delco Professional model. You may have some fitting issues so thats worth keeping in mind but not as bad as having a V8 engine stuffed in versus the V6.

We put an Optima Red Top battery in my son's '08 GXP but it was a PITA to install but we eventually got it to fit. :grinyes:

Mine does that occasionally but I have the voltage booster and alternator rewire. not sure if you have those though. in both of my 04s before I installed the vbooster,once in a while after initial startup it would come on then go back to normal.