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Discussion Starter · #1 ·
I was driving my G8 today and the display popped up with "Service Charging System" .. is there a way to scan this for specific code? I have a 2000 watt class D amp and 2 12s that drain the system pretty badly. I noticed when I turned the car back on the message was gone but I just wanted to get ahead of this before it causes more problems.

What specifically does this message mean? Is it tied to alternator output or what?

Also, I was reading about "fuel economy mode" with the alternator. Is there a way I can turn that off? I don't drive this thing every day so fuel economy really isn't an issue. I need the amps more than fuel economy.

I've attached the likely culprit who blew up my alt lol 2 x Rockford fosgate P3s and a Skar 2000.1D

=D
184555


metatags: G8 Service Charging System Light
 

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More or less, there's a "fault" in the battery charging system. Are you using the stock GT alternator? Besides checking the battery and alternator connections, check the battery ground bolt. https://www.g8board.com/threads/battery-ground-bolt-read-and-check-yours.224746/. Bear in mind, it's highly possible the alternator will need to be upgraded to one generating more amperage if you plan on keeping the sound system setup.
 

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If the alternator is replaced, ensure it's a genuine AcDelco unit preferably new as many aftermarket's are notorious for being problematic. Also, where/how is the amp grounded?
 
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Kindly suggest creating a separate ground for the amplifier. The stock GT alternator (92191127) is rated at 140 amps while the Caprice PPV alternator (92258220) is rated at 170 amps.
 

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Do your volts drop to 12 when running? Alternator. Or is starting a struggle? Battery.
 

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How old/new is the battery? Brand/line? About how long does the car sit between uses? By the way, "fuel economy mode" is a body control module function. Can troubleshoot the charging system, but it won't "generate a code" like the engine/transmission modules. Who installed the sub-woofers and amplifier?
 

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You can try going into engineering mode and looking at the battery charge level. If that is low, I would think it turns on that warning.
 
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Powermaster makes a good alternator. I put a 175 amp in my '96 Dakota work truck to handle the electric cooling fans and stereo with the a/c running full force. I've got nice bright headlights now, too. I tried running underdrive pulleys, but the alternator didn't put out enough at idle to maintain through a long traffic light. Where I'm going with this is, could you put a larger pulley on your existing alternator to raise it's output slightly at idle to avoid the "service charging system" light and carry the extra electrical load of the stereo system, rather than replacing the alternator that's probably just fine? It seems to me to be a cheaper alternative, and changing the alternator may not help anyway.
 

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For what it's worth, aftermarket alternators are notorious for causing issues/glitches with the G8's electrical system. As a result, always suggest purchasing a new, genuine AcDelco unit.
 

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For what it's worth, aftermarket alternators are notorious for causing issues/glitches with the G8's electrical system. As a result, always suggest purchasing a new, genuine AcDelco unit.
I understand that very well, Pony Man. I've had my share of problems with badly built or rebuilt parts. Especially in the last five to ten years. I wish I still had the equipment on which my father taught me to rebuild starters and generators when I was a kid. When I suggested Powermaster, it was because I've done business with them for some time now, and I've gotten to know the folks. They do put out a quality product and stand behind everything they do. I'm surprised you didn't catch the big mistake I made in my response yesterday. The replacement pulley size should be smaller, not larger, to correct and undercharge at idle. A shorter belt may be needed, also.
 

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Have yet to hear of one aftermarket alternator that goes well with the G8, but such is not to say they're non-existent. Rather err on the side of caution, purchase a new oem and hopefully it's a one and done. Can always edit the post by selecting the three dots in the upper right. Edit. Make corrections. Save.
 

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Note that some owner have had problems with higher amperage alternators on they're G8's.
Gave the car fits until they put a stock amperage alternator back on.
No one ever figured out why this can happen but something to be aware of.
 

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Discussion Starter · #16 ·
As an update, I haven't seen this message since the day that I had a guy fix something to do with the AC clutch. It was making a squeeking noise and the car was already at his shop for LCA replacement and he also replaced a wheel bearing that had several broken studs; I had him also fix the squeeking noise. I wonder if this was an issue with the belt slipping from some type of lube on the AC clutch.

Also, I think a big part of this has nothing to do with the grounding; I think that the subsonic cutoff on my amplifier was too low which resulted in super low bass being amplified in a ported box.

I actually swapped the + - to give the subs a 180 phase shift and set the subsonic (HPF) to ~28hz. I also am more careful with leaving the bass on the stock headunit turned up all the time. I give the subs/charging system/amp a lot of breaks now.

This seems to be working extremely well. I had one day before I did all this where my battery was almost dead by the time I got to my destination. I think it was the lack of subsonic HPF setting that really drained the battery. My amp was also sliding around at the time and it was dangerously close to the range of the subwoofer drive (physically). I applied some velcro to the bottom of the amp and set it as far back in the trunk as possible.

I think the stock alternator works fine now for my 2000.1D skar amp and 2 12 Rockford fosgate P3. The key is dialing it in, but the truck is PERFECT for this setup. I was barely able to fit that massive ported box in the trunk but with a 180 phase shift and stock head unit (line level converter off the stock trunk amp) this thing hits as hard as I need it to. gotta love that trunk space!

But yeah, still curious exactly what "service charging system" means... however, in my case I think the amp was just poorly tuned and the setup was wrong, which was draining the system excessively. Thanks for all the responses!
 
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