Newbie Voltage Question

[hivolt]

Hello everyone. I have a 2005 ext. cab Chevy with the 4.8. The problem I have been having is the voltage gauge in the dash seems to be fluctuating from approximately 11 volts to over 14. When the truck is idling, the gauge will slowly move around in this range, up and down. Has anyone else had this problem? I took it to the dealer since it is still under warranty, and they gave the "it's in normal operating range" explanation. They checked the alternator and said it is putting out the correct voltage of 13.8 to 14 volts. However, I have had several GM trucks and have never had one act like this. Any help you guys could give would be greatly appreciated. By the way, I have been lurking on this site for a while now and have gotten much good advice. Thanks for all the help!

[pm26]

For comparison, my '06 Z71 (5.3 engine) voltage fluctuates between about 12.5 Volts and 15 Volts. It does not fluctuate back and forth, but stays at any voltag setting for a while. I have not seen the gauge drop below the 12 volt treshold yet, but the gauge scale divisions are really illogical so you cannot tell exactly at a glance what voltage each segment represents.

 

If you had your alternator checked, I would not worry. The gauge may not be super accurate. You can periodically check the alternator output yourself by using a simple digital multimeter (can purchase in any auto parts store for about $ 10). Just select direct current voltage setting on the multimeter, connect leads to the battery terminals, start the engine and watch the voltage. If you turn accessories, such as lights on, the voltage will drop somewhat.

[I-H8-4Ds]

I had an 03 and its gage stayed on 14 volts all the time. When I bought my 05, I noticed that my voltmeter slowly fluctuated up and down. I was told that on the newer models, they shut the alternator off completely when the battery becomes fully charged, rather than constantly maintaining a low rate steady charge. The idea is to reduce engine load and thus improve mpg.

[GM-Tech]

Volt Gauge Fluctuation - keywords cluster electrical excessive fluctuation gage generator intermittent IPC operation volt voltage voltmeter wire #PIT3331A - (Dec 16, 2005)

 

 

2005-2006 Cadillac Escalade Models

 

2005-2006 Chevrolet Avalanche, Silverado, Suburban, Tahoe

 

2005-2006 GMC Sierra, Yukon Models

 

with RVC

 

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

 

Condition/Concern:

Some customers may comment that their voltmeter is fluctuating between 12 and 14 volts on their full size pickup / utility vehicle.

 

Recommendation/Instructions:

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 turns off the alternator when it is not required in order to improve fuel economy. The alternator will turn back on when additional voltage is required. This will cause the voltmeter to fluctuate between 12 and 14 volts as opposed to non-regulated systems which 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.

 

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

 

 

 

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.

 

 

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[hivolt]

Thanks for all the help. I guess I was just used to the steady 14 volts all the time.

[rmreid]

I am having this same issue with my '06 Silverado, after doing a search and finding this thread I realize that it is not an issue afterall

[NothinButBowTies]

What I want to know if the monitoring system is in the alternator or a PCM function. I woud like to have this my 03. Every bit helps!

[Mfishing2]

Volt Gauge Fluctuation - keywords cluster electrical excessive fluctuation gage generator intermittent IPC operation volt voltage voltmeter wire #PIT3331A - (Dec 16, 2005)

 

 

2005-2006 Cadillac Escalade Models

 

2005-2006 Chevrolet Avalanche, Silverado, Suburban, Tahoe

 

2005-2006 GMC Sierra, Yukon Models

 

with RVC

 

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

 

Condition/Concern:

Some customers may comment that their voltmeter is fluctuating between 12 and 14 volts on their full size pickup / utility vehicle.

 

Recommendation/Instructions:

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 turns off the alternator when it is not required in order to improve fuel economy. The alternator will turn back on when additional voltage is required. This will cause the voltmeter to fluctuate between 12 and 14 volts as opposed to non-regulated systems which 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.

 

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

 

 

 

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.

 

 

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I am seeing the fluctuation on the gage also. But should the system be turning down the charging at night when the lighs are on & possibly the heater fan motor?

[Sierrawolf]

I been haveing that with my 03 sierra and i still haveing that problem even when i changed out the alternator. I hurd their is something you could programed in the truck CPU to stop that. I just wounder if that is true.