Voltage Guage

[Whylee]

I have an 08 Sierra and i have noticed the volt guage fluctuates. When started cold it reads approx 12..then when I drive for a bit it reaches 14..then it seems to fluctuate between 13 and 14 . Is this normal or is there a problem? Thanks in advance!

[07-Z71]

My 2007 NBS does this as well.... I think there is a TSB? anyone?

[hubbycap]

As I understand it, this is normal. The Active Fuel Mgmt, AFM, pulls every trick possible including shutting down the alternator when in the V4 mode. Monitoring the battery charge level, it will bring the alternator on line (along with V8 mode to power it) if battery voltage falls too low. Unless you have experienced a dead battery, which there IS a TSB for, ignore these normal range fluctuations.

[PhilB]

This should be normal. In the owner's manual for the GMT900 trucks:

 

Electric Power Management

This vehicle has Electric Power Management

(EPM) that estimates

the battery’s temperature and state of charge. It

then adjusts the voltage for best performance

and extended life of the battery.

When the battery’s state of charge is low, the

voltage is raised slightly to quickly put the charge

back in. When the state of charge is high, the

voltage is lowered slightly to prevent overcharging.

If the vehicle has a voltmeter gage, you may

see the voltage move up or down. This is normal.

If there is a problem, an alert will be displayed.

 

Hope this helps.

Phil

[Whylee]

This should be normal. In the owner's manual for the GMT900 trucks:

 

Electric Power Management

This vehicle has Electric Power Management

(EPM) that estimates

the battery's temperature and state of charge. It

then adjusts the voltage for best performance

and extended life of the battery.

When the battery's state of charge is low, the

voltage is raised slightly to quickly put the charge

back in. When the state of charge is high, the

voltage is lowered slightly to prevent overcharging.

If the vehicle has a voltmeter gage, you may

see the voltage move up or down. This is normal.

If there is a problem, an alert will be displayed.

 

Hope this helps.

Phil

 

Thanks for the great info Phil...I knew I should have read the manual...new technology..ya got love it..I think!

[MS3DALE]

Document ID# 2042756

 

 

Subject: Information on Voltmeter Gauge Fluctuation Due to Regulated Voltage Control System and Concerns About Camper/Trailer Battery Charging #07-06-03-009 - (12/05/2007)

 

 

 

Models: 2005-2008 Cadillac Escalade Models

 

2005-2008 Chevrolet Avalanche, Silverado, Silverado Classic, Suburban, Tahoe

 

2005-2008 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.

 

 

 

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

 

 

© Copyright General Motors Corporation. All Rights Reserved.

[Whylee]

As I understand it, this is normal. The Active Fuel Mgmt, AFM, pulls every trick possible including shutting down the alternator when in the V4 mode. Monitoring the battery charge level, it will bring the alternator on line (along with V8 mode to power it) if battery voltage falls too low. Unless you have experienced a dead battery, which there IS a TSB for, ignore these normal range fluctuations.

 

 

I thought maybe it had something to do with all this new technology ..thanks for the info and clearing it up...

[Whylee]

Document ID# 2042756

 

 

Subject: Information on Voltmeter Gauge Fluctuation Due to Regulated Voltage Control System and Concerns About Camper/Trailer Battery Charging #07-06-03-009 - (12/05/2007)

 

 

 

Models: 2005-2008 Cadillac Escalade Models

 

2005-2008 Chevrolet Avalanche, Silverado, Silverado Classic, Suburban, Tahoe

 

2005-2008 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.

 

 

 

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

 

 

© Copyright General Motors Corporation. All Rights Reserved.

 

thanks for the help and great info..I can't keep up with all this technology...

[rcbgn00]

This info in similar to something I just saw this morning. Every since I bought the truck the voltage was rock solid at about 15v and never moved. Today when I took a drive the voltage dropped to around 12 and stayed there. When I restarted the truck after the first stop it went back up to the 15v it used to ride at but then as I drove it slowly dropped back to about 12v. I did notice the interior lights were dimmer like they should at a lower voltage.

 

Anyone know whats up and why the sudden change?