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Gauge on Voltmeter Fluctuates... Come Inside

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Old 05-09-2009, 09:21 PM   #1
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Question Gauge on Voltmeter Fluctuates... Come Inside



I had a buddy install my aftermarket switch for my cut and run wiring for my fans.

Now ever since i run the car with the lights on (have not driven it during the day to notice) but the needle on my voltmeter flucuates and dances. It will be normal when driving at about 14v, then when i am approaching a stop light and put the car in nuetral the voltmeter dips to about 10v the lights dim then it will come back up to 14v and the lights will brighten back up. When i am driving the needle dances a bit??????? ALL my lights (headlight lights, gauge cluster lights, HVAC lights and headlights) flicker and dance around. Again i noticed this AFTER i installed the switch plate.

What is causing something to be drawing power? Is my alt going bad? No i do not have an UDP on my alt....

Please someone help me.

Ohh yea i did notice that i had a little bit of rust on + battery cable, but i took a wire brush and got rid of it all. Seem to fix it but now the problem is back

Thanks for the help
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Old 05-09-2009, 09:32 PM   #2
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I had this problem when my car was stock, and I still have it. I'd be interested in hearing what everyone has to say.
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Old 05-10-2009, 02:40 AM   #3
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I visted my buddy tonight, i started the car (idle) and he saw the lights flickering/dancing.. Then i held the revs at about 1500 RPMs all lighs were on (headlights lights, actual headlights, HVAC, gauge cluster and radio) and he saw again the lights were all flickering/dancing and he saw the voltmeter needle dancing back and fourth. The voltmeter gauge said 14v-15v. I let the idle return to normal, voltmeter dropped to 10v-11v then back to 14v. When it dropped to the low volts ALL lights that i mentioned above all dimmed down and then when the voltmeter raised to 14v again ALL lights brightened up again.

He said that a diode on the alt could be going bad.

Anyone else have anyideas??????
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Old 05-10-2009, 03:01 AM   #4
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Mine does the same thing and it seems to be a common complaint here. I believe that it is a problem with the stock alternator.
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Old 05-10-2009, 08:59 AM   #5
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Get the alternator rebuilt or replace it. Those are classic symptoms of a failing alternator.
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Old 05-10-2009, 12:25 PM   #6
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hello, i'm not driving a camaro but i've got a 2005 avalanche with a 5.3...when i bought it i had the same issue as your discribing, i to thought it was the battery or alternator so after having those replaced under warrenty i found out it wasn't...what i found was the issue is something i've traced to be called a generator control module...guess it works the same as the regulator on the alternator... but anyway, there was a 10 or 12 pin connector going to a black box that sat on my negative batter wire close to the battery. i found out that when they fail they are set to defult to 13.8 volts. so i unpluged it and never had the problem again...now i'm just waiting for my battery light on my cluster to die lol... from GM it's about a $300 part which in my opinion isn't needed
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Old 05-10-2009, 01:38 PM   #7
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Get the alternator rebuilt or replace it. Those are classic symptoms of a failing alternator.
I had a feeling that the alt was dying on me. I guess it is time for an upgrade..

Should i get a stock replacement? Or should i go with a higher amp one?
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Old 05-10-2009, 01:39 PM   #8
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Originally Posted by Fbodyfan View Post
Mine does the same thing and it seems to be a common complaint here. I believe that it is a problem with the stock alternator.
Thank you for the input. I think i will replace the alt and see if that is the issue.

I do not think that it is the battery as i have a Optima Red top that i bought 2/2007 and when i store the car i disconnect it from the car and bring it inside the house.
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Old 05-10-2009, 01:44 PM   #9
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Originally Posted by 95highline View Post
hello, i'm not driving a camaro but i've got a 2005 avalanche with a 5.3...when i bought it i had the same issue as your discribing, i to thought it was the battery or alternator so after having those replaced under warrenty i found out it wasn't...what i found was the issue is something i've traced to be called a generator control module...guess it works the same as the regulator on the alternator... but anyway, there was a 10 or 12 pin connector going to a black box that sat on my negative batter wire close to the battery. i found out that when they fail they are set to defult to 13.8 volts. so i unpluged it and never had the problem again...now i'm just waiting for my battery light on my cluster to die lol... from GM it's about a $300 part which in my opinion isn't needed
Does my car, on the neagtive terminal have that same wire that you are talking about?
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Old 05-10-2009, 05:08 PM   #10
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i don't know. i know it's something GM had put on a number of there vehicles that were harder on gas...there theory behind this box is it would help the life of the battery and "improve" gas milage...
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Old 05-10-2009, 09:00 PM   #11
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Thank you for the input. I think i will replace the alt and see if that is the issue.

I do not think that it is the battery as i have a Optima Red top that i bought 2/2007 and when i store the car i disconnect it from the car and bring it inside the house.
ive never had any luck with optima batteries. We have replaced many of them at work. Kenetic batteries work decent, but have a had time turing over large cubic inch motors 8.0 liters and bigger.

Sounds like your problem is in the alternator, because the problem changes by RPM.
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Old 05-10-2009, 09:37 PM   #12
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ive never had any luck with optima batteries. We have replaced many of them at work. Kenetic batteries work decent, but have a had time turing over large cubic inch motors 8.0 liters and bigger.

Sounds like your problem is in the alternator, because the problem changes by RPM.
Yeah i do not think it is my battery. I will have my buddy test it out and my alt out for me
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Old 05-11-2009, 09:19 AM   #13
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I had a feeling that the alt was dying on me. I guess it is time for an upgrade..

Should i get a stock replacement? Or should i go with a higher amp one?
I had mine rebuilt to stock specs by a local repair shop. It was ~$50 to have it done off of the car. If you don't have any major AV upgrades stock should be fine.

From the posts I have read, you want to stay away from AutoZone alternators. They seem to have a high rate of failure. Even though they have a lifetime warranty it still takes time and labor to get them replaced.
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Old 05-11-2009, 09:22 AM   #14
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Originally Posted by 95highline View Post
hello, i'm not driving a camaro but i've got a 2005 avalanche with a 5.3...when i bought it i had the same issue as your discribing, i to thought it was the battery or alternator so after having those replaced under warrenty i found out it wasn't...what i found was the issue is something i've traced to be called a generator control module...guess it works the same as the regulator on the alternator... but anyway, there was a 10 or 12 pin connector going to a black box that sat on my negative batter wire close to the battery. i found out that when they fail they are set to defult to 13.8 volts. so i unpluged it and never had the problem again...now i'm just waiting for my battery light on my cluster to die lol... from GM it's about a $300 part which in my opinion isn't needed
That's interesting. My 07 Avalanche has a couple of minor issues including flickering lights at idle. I have plans to take it in to the dealer today for warranty work. I will mention this to them and see what they say. Maybe I can get more info on this.

EDIT: Dealer confirmed what Highline said on my 07 Avalanche. In an effort to increase MPG they kink the alternator in and out. Good ol' GM quality for ya. There is nothing they can do to fix it. In the newer vehicles this is controlled by the BCM not a separate module. I do not believe the 4th gen F-body does this at all. The new 5th gen might.
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Old 05-11-2009, 10:53 AM   #15
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I had a feeling that the alt was dying on me. I guess it is time for an upgrade..

Should i get a stock replacement? Or should i go with a higher amp one?
... or your serpentine belt. When was the last time you checked/replaced it? Have you checked the index on the tensioner pulley?
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Old 05-11-2009, 11:16 AM   #16
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... or your serpentine belt. When was the last time you checked/replaced it? Have you checked the index on the tensioner pulley?
I am runing a goodyear gatorback belt. I put it on 2/2007 car is not a DD. Have not checked my idler pulley
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Old 05-11-2009, 11:24 AM   #17
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Don't always trust the gauge either....if you have a multi meter, check the battery voltage using that.
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Old 05-11-2009, 11:35 AM   #18
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Don't always trust the gauge either....if you have a multi meter, check the battery voltage using that.
I do not trust the gauge, but i know something is going on when at idle the lights are dancing and wheni give it gas and the idle comes back down and the needlw goes from about 14-15v down past the 13v indicator and ALL the lights dim
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Old 07-08-2009, 02:23 AM   #19
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well guys im gonna join your club on this issue!
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Old 07-26-2009, 01:30 AM   #20
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Don't always trust the gauge either....if you have a multi meter, check the battery voltage using that.
I was testing my battery with a voltmeter on Friday. With the car idling, headlights on, radio on, A/C on and hazards on the voltmeter read 13.8-13.9

I still think it is going to be my alt. Battery is fine..

Here is the kicker sometime my car will be fine where the needle wont move, then it has days were I am coming up to stop sign and the needle will drop to 10v

The next time i have my car out, i will try to take a vid and post it
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Old 07-26-2009, 01:30 AM
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