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Discussion Starter · #1 ·
It was thought by a reliable shop, the alternator was bad, but two replacements resulted in the same thing - charging voltage is varying with too much variation as observed in the engineering mode. Alternator output swings from 13.4-5 to as much as 15 volts. Battery will run down in a day or so; the battery saver icon will show-up on the DIC and the A/C will shut off, etc. The mechanic thought the negative battery low voltage sensor was bad, but there are none available for replacement. I don't even know what it looks like. Maybe someone reading this will possibly know of someone acquiring wrecks who might have one of those available.

Need some help here G8 GT owners!!!

grandpop09
 

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Where did you get these? AutoZone?

Did you try a Genuine GM Alternator? The G8 does not like aftermarket brands.
 
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Like Oldpoop55 said you need to make sure it's a new OEM or AC Delco.
 
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What were the initial symptom(s) with the vehicle? Are they different from the current issues? Brand and age of battery?
 

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Aside from a bad clamp, what about hidden corrosion inside the ground cable? I've seen it happen in a few other cars. Is your vent tube properly attached and sealed w/teflon tape? I had a friend replace everything but the ground cable in his truck because he wouldn't believe me... until he replaced it - then he did... Also happened with my 2000 Mustang GT after only five years of age.
 

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It was thought by a reliable shop, the alternator was bad, but two replacements resulted in the same thing - charging voltage is varying with too much variation as observed in the engineering mode. Alternator output swings from 13.4-5 to as much as 15 volts. Battery will run down in a day or so; the battery saver icon will show-up on the DIC and the A/C will shut off, etc. The mechanic thought the negative battery low voltage sensor was bad, but there are none available for replacement. I don't even know what it looks like. Maybe someone reading this will possibly know of someone acquiring wrecks who might have one of those available.

Need some help here G8 GT owners!!!

grandpop09
If indeed this is the problem and I am not sure that it is. Look at the attached photo. It is of the negative battery lead that connects from the negative battery terminal to the frame of the vehicle, This is a VE Commodore 2008, V8 so it should be the same for a G8. There is a separate battery current sensor that the cable passes through. This is also known as a current transformer or current clamp.

Also I have attached what came up when googled VE Commodore Battery Sensor, it shows the AC Delco Part for GM, and in the USA.........try that. Looks the same as the photo of the one on my car

But I would be looking around the wiring, connector on the battery current sensor first. Make sure it's there!


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Discussion Starter · #7 ·
If indeed this is the problem and I am not sure that it is. Look at the attached photo. It is of the negative battery lead that connects from the negative battery terminal to the frame of the vehicle, This is a VE Commodore 2008, V8 so it should be the same for a G8. There is a separate battery current sensor that the cable passes through. This is also known as a current transformer or current clamp.

Also I have attached what came up when googled VE Commodore Battery Sensor, it shows the AC Delco Part for GM, and in the USA.........try that. Looks the same as the photo of the one on my car

But I would be looking around the wiring, connector on the battery current sensor first. Make sure it's there!


View attachment 188558
Thanks for your reply. However, when I go to the site that is referenced and check the product application, it says it does not fit my car. So, I don't know what to think. My car is still at a shop that has given up, so i am picking it up today and will take a look at the setup, etc. Thanks again for your time and suggestions!

grandpop09
 

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OK.

So if I was at this point. I would ring or go into a GM Dealer Spare Parts Dept.

I would ask them for a Battery Current Sensor for????? Pontiac G8? V8? V6?

Give them the VIN Number and Model and ask them to look it up.

If they don't have one can they get one?

If I they can't get one ask for the Part Number for either the GM original or AC Delco so that you can source it.

These are about $20 by the looks.
 

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Discussion Starter · #9 ·
Thanks again. I will first look at mine and take a picture to show a parts guy and have him look up what might be available. I will also check my ground connection to be sure I don't have the rust "gremlin" at the frame connection. The problem I'm having is the alternator voltage varies too much and on average does not provide enough current to keep the battery charged. The battery has checked good and with a battery charger it reaches 98 percent charge and essentially holds there when left static. After starting the car, it isn't long before the draw on the battery exceeds the rate of charge from the alternator - 2 were installed with same results. I love these cars - I have 2 - the 2009 PBM and a 2008 IOM.

grandpop09
 

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Do you know the Brand of the 2 alternators installed?
 

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Aftermarket alternators are notoriously problematic communicating with the G8's charging system. Would return the rebuilt units. Purchase and install genuine preferably new AcDelco alternators. Remanufactured AcDelco known as gold/professional series parts are hit-n-miss.
 

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Definetly replace with new OEM or new AC Delco.
 

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100 % on GM OEM alternator, the internal regulator of the rebuilt versions do not communicate with the ECM if at all, and GM does not give out those specs to aftermarket versions. also be sure to specify if it is a 09 or 09.5 as all modules are different from both
 
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