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Voltage Fluctuation ?


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#1 BADASS07SILVERADO

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Posted 05 January 2011 - 09:05 PM

When I start my truck my volatge goes up to just above 14 volts. After about 7 - 10 minutes, the voltage goes down to exactly 12.7 volts. The truck still runs fine and the volts dont move again untill I re-start the truck. Is my alternator going bad or is this normal for a 2007 Silverado 5.3?

#2 MS3DALE

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Posted 05 January 2011 - 09:09 PM

Its normal....

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Service Information 2007 Chevrolet Silverado - 4WD | Sierra, Silverado VIN C/K Service Manual | Document ID: 2394671
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#07-06-03-009B: Information on Voltmeter Gauge Fluctuation Due to Regulated Voltage Control System and Concerns About Camper/Trailer Battery Charging - (Feb 5, 2010)


Subject: Information on Voltmeter Gauge Fluctuation Due to Regulated Voltage Control System and Concerns About Camper/Trailer Battery Charging


Models: 2005-2010 Cadillac Escalade Models

2005-2010 Chevrolet Avalanche, Silverado, Silverado Classic, Suburban, Tahoe

2005-2010 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 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.

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#3 music

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Posted 05 January 2011 - 09:12 PM

Excellent info Rich. I didn't know that the GM system operated this way.

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#4 BADASS07SILVERADO

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Posted 06 January 2011 - 07:32 PM

WOW. Thank you! This forum is great!

#5 banuelos46

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Posted 25 January 2012 - 03:27 PM

so does your truck still do this? or did you fix something?? I bought a 07 sierra 3 months ago and it read 14 for those months then i replaced the battery and ever since then in is constantly up and down most of the time under 14 and latelyt been reading 12.7 also. thanks




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