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Random voltage drop. Alternator taking a dump?

random voltage drop alternator taking dump

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#1 OFFLINE   04-2500HD

 
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Posted 28 June 2015 - 01:29 AM

In my 2500hd I have noticed (during night time driving mainly). The voltage in the whole truck drops suddenly. I'm thinking right around 12v. It stays like that for a second or two then pops right back up to 14.

I have only noticed this during the night because my headlights and interior illumination lights dim down at the same time. I don't notice it during the day.

It acts like when I have the plow on and try to move it. Lights dim, gauge drops then pops right back.

It will do it with minimal load on alt. ( all lights off). Or with hi 6 lights on.

It's completely random, sometimes it won't do it and other times it can do it 3 times in a minute.


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#2 OFFLINE   AA1PR

 
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Posted 28 June 2015 - 07:33 AM

In my 2500hd I have noticed (during night time driving mainly). The voltage in the whole truck drops suddenly. I'm thinking right around 12v. It stays like that for a second or two then pops right back up to 14.

I have only noticed this during the night because my headlights and interior illumination lights dim down at the same time. I don't notice it during the day.

It acts like when I have the plow on and try to move it. Lights dim, gauge drops then pops right back.

It will do it with minimal load on alt. ( all lights off). Or with hi 6 lights on.

It's completely random, sometimes it won't do it and other times it can do it 3 times in a minute.


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are all the battery connections tight?

 

no shorts anywhere ?


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#3 OFFLINE   04-2500HD

 
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Posted 28 June 2015 - 09:24 AM

I haven't noticed any but I'll check


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#4 OFFLINE   04-2500HD

 
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Posted 28 June 2015 - 12:35 PM

Connections are tight, clean. Didn't see any blown fuses, I unhooked plow wiring from battery just to be sure I'll find out the next time I drive it at night when it's most noticeable


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#5 OFFLINE   DirtRidinZ71

 
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Posted 28 June 2015 - 05:31 PM

I used to notice my old 02 work truck did this from timeand my 05 trailblazer does the same thing. No real pattern or reason to cause it either.
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#6 OFFLINE   04-2500HD

 
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Posted 29 June 2015 - 05:50 PM

It's annoying as hell though


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#7 OFFLINE   AA1PR

 
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Posted 29 June 2015 - 08:28 PM

It's annoying as hell though


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my old alternator did it from time to time as well


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#8 OFFLINE   04-2500HD

 
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Posted 29 June 2015 - 09:21 PM

I hope it's not the alt. I replaced it less than a year ago


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#9 OFFLINE   04-2500HD

 
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Posted 29 June 2015 - 09:23 PM

But if it is I guess it should be under warranty


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#10 OFFLINE   magimerlin

 
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Posted 05 July 2015 - 09:08 PM

Look at your negative cable from your battery... does it have a round sensor around the cable with a bunch of wires going to it.. if so it's basically a hall effect sensor....

This says 05 but I've seen them in 04 and 03 as well.... copied from another site.

----Subject: Information On Voltmeter Gauge Fluctuation Due To Regulated Voltage Control System And Concerns About Camper/Trailer Battery Charging 


Models: 2005-2009 Cadillac Escalade Models 

2005-2009 Chevrolet Avalanche, Silverado, Silverado Classic, Suburban, Tahoe 

2005-2009 GMC Sierra, Sierra Classic, Yukon Models 


Voltmeter Fluctuation Condition:
Some customers may comment that the voltmeter is fluctuating between 12 and 14 volts on their full size pickup or utility vehicle. Starting with the 2005 model year, light duty full size pickups and utilities are equipped with a new Regulated Voltage Control (RVC) system. This system reduces the targeted output of the generator to 12.6-13.1 volts when in "Fuel Economy Mode" to improve fuel economy. The generator may exit "Fuel Economy Mode" if additional voltage is required. This will cause the voltmeter to fluctuate between 12 and 14 volts as opposed to non-regulated systems that usually maintain a more consistent reading of 14 volts. This fluctuation with the RVC system is normal system operation and NO repairs should be attempted. 

Camper/Trailer Battery Charging Concerns:
Some customers may comment that when towing or hauling a camper/trailer, the auxiliary battery for the camper/trailer will not stay charged. In most cases, this concern is blamed on the new RVC system. While the RVC system does reduce the generator's targeted output voltage to 12.6-13.1 volts when in "Fuel Economy Mode", this feature is bypassed if the tow/haul feature is enabled. With the tow/haul feature enabled, the RVC system will stay in "Charge Mode" and the targeted generator output voltage will be 13.9-15.5 volts, depending on the battery state of charge and the estimated battery temperature. To keep the generator in the "Charge Mode", use either of the following two methods.

• The first method is to use the tow/haul mode when towing or hauling a camper or trailer. 

• The second method is to turn on the headlights, which will increase the generator's targeted output voltage to 13.9-14.5 volts.



sent from what use to be a great nation...



#11 OFFLINE   04-2500HD

 
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Posted 06 July 2015 - 08:40 AM

I'll check once I get home, and whenever it stops pouring


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#12 OFFLINE   04-2500HD

 
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Posted 06 July 2015 - 10:49 AM

I do not have that on my negative cable.


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#13 OFFLINE   Hedge

 
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Posted 06 July 2015 - 05:34 PM

Any chance the voltage decreases when the engine bay is warm and/or hot?  Resistance due to heat can drop voltage esp at idle, then when you step on the gas it pops back up.

 

This used to happen to my '99 at traffic lights in the summer.



#14 OFFLINE   04-2500HD

 
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Posted 06 July 2015 - 08:16 PM

This will happen going 0mph-60mph. Definitely not an idle only issue


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#15 OFFLINE   GlitchMobile

 
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Posted 29 November 2015 - 11:09 AM

I have a very similar situation with my 2003 Subrban too. Just started happening this summer. Replaced the alternator, still same problem. Happens in the daytime too, I can hear it affect the dashboard blower fan.

 

Have you solved the gremlin?







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