Alternator/voltage
Thread Starter
Intermediate
Joined: Mar 2014
Posts: 33
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From: Houston Texas
Alternator/voltage
Hey all, I've read a few threads on this and am a bit up in the air after reading regarding what the issue actually is, so I'm starting this thread to get your thoughts.
Car is 2006 C6Z. The voltage varies considerably while driving - while cruising/rpm's above idle it will be in normal range and then at idle it will hunt all over the place, but generally trending low, and dipping in to the 12's so as to every once in a while cause the DIC to prompt: "Service Charging System."
I changed the battery as a step one (it was old) and at the same time had the alternator tested at Autozone (actually took it out and handed it to them to test). It passed their tests...
So, with the new battery and the original alternator bolted back up, it's still acting as I described above (albeit with the voltage generally being higher, but still dipping into 12's sometimes).
Can we confidently conclude it's the alternator that's out, e.g. the regulator?
Thoughts? Thanks!
Car is 2006 C6Z. The voltage varies considerably while driving - while cruising/rpm's above idle it will be in normal range and then at idle it will hunt all over the place, but generally trending low, and dipping in to the 12's so as to every once in a while cause the DIC to prompt: "Service Charging System."
I changed the battery as a step one (it was old) and at the same time had the alternator tested at Autozone (actually took it out and handed it to them to test). It passed their tests...
So, with the new battery and the original alternator bolted back up, it's still acting as I described above (albeit with the voltage generally being higher, but still dipping into 12's sometimes).
Can we confidently conclude it's the alternator that's out, e.g. the regulator?
Thoughts? Thanks!
Team Owner
Joined: Nov 2007
Posts: 24,035
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From: Gilbert AZ
One other option is the tensioner or belt is slipping. I would put a fresh belt/tensioner on and see if that helps. Cheap to do anyways.
Odds are the alternator is probably bad. Mine use to be ~12.5-13.0 then I went to one of the billet tech ones and now it is a rock steady 14.3V.
Odds are the alternator is probably bad. Mine use to be ~12.5-13.0 then I went to one of the billet tech ones and now it is a rock steady 14.3V.
Race Director
Joined: Aug 2005
Posts: 13,592
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From: Hudson WI
NCM Sinkhole Donor
One other option is the tensioner or belt is slipping. I would put a fresh belt/tensioner on and see if that helps. Cheap to do anyways.
Odds are the alternator is probably bad. Mine use to be ~12.5-13.0 then I went to one of the billet tech ones and now it is a rock steady 14.3V.
Odds are the alternator is probably bad. Mine use to be ~12.5-13.0 then I went to one of the billet tech ones and now it is a rock steady 14.3V.
Team Owner
Joined: Oct 2004
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From: San Clemente CA
Race Director
Joined: Aug 2005
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From: Hudson WI
NCM Sinkhole Donor
Burning Brakes
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From: westminster California
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Pro
Joined: Jan 2014
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From: NEWPORT NEWS VIRGINIA
OP I had the same issue, but after trouble shooting I have a 25% ud pulley balancer, and realize i needed an overdrive pulley for the alternator as it caused my issues to bounce from 12 to 13.8 volts causing the service charging system light at times also. Tsp has them for cheap.
Race Director
Joined: Aug 2005
Posts: 13,592
Likes: 187
From: Hudson WI
NCM Sinkhole Donor
OP I had the same issue, but after trouble shooting I have a 25% ud pulley balancer, and realize i needed an overdrive pulley for the alternator as it caused my issues to bounce from 12 to 13.8 volts causing the service charging system light at times also. Tsp has them for cheap.
Pro
Joined: Jan 2014
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From: NEWPORT NEWS VIRGINIA
Thread Starter
Intermediate
Joined: Mar 2014
Posts: 33
Likes: 0
From: Houston Texas
Factory pulleys on my car. I wonder the tune on the car to accommodate the cams has the idle set too low for the factory alternator? Is there a minimum ideal charging rpm that anyone knows of?
Thread Starter
Intermediate
Joined: Mar 2014
Posts: 33
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From: Houston Texas
Well here's a rather frustrating update. Having concluded that the problem must be the factory alternator since the voltage was still dipping drastically when not cruising, I replaced it with another factory alternator. It's still doing the exact same thing!
So I now have 1) a brand new battery; 2) a brand new alternator; and 3) voltage that keeps dipping into the 12's at idle (and the DIC says "Service Charging System."
I'm now at a loss. Any thoughts?
So I now have 1) a brand new battery; 2) a brand new alternator; and 3) voltage that keeps dipping into the 12's at idle (and the DIC says "Service Charging System."
I'm now at a loss. Any thoughts?
Team Owner
Joined: Mar 2008
Posts: 21,502
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From: Southern Utah
The alternator voltage is controlled by the BCM, not an internal regulator. Since the output of an alternator drops off rapidly as its' speed goes down, my bet is that it is spinning a bit too slowly at idle. A slightly smaller pulley would help, but as long as it charges OK when you are actually driving, I wouldn't get too worried about it.