dash voltmeter fluctuations

I-H8-4Ds · September 14, 2005

Hello,

I have a 2005 Silverado, 4.8 liter, automatic, still under warranty. I have noticed that my voltmeter reading will sometimes vary between what looks like 12 to 15 volts. It does not happen quickly, but usually within a 15 minute time frame of steady highway driving. No signs yet of a low battery when starting, either.

I would probably not be concerned, except my 2003 truck was always nailed dead on at 14.

Was a change made to accomodate a different type of battery? Could my electric radiator fans draw the voltage down? Just a guess there.

Thank you for your advice.

Dan

GM-Tech · September 14, 2005

05 Chevrolet/GMC/Cadillac All Full Size Trucks with Regulated Voltage Control Gauge Fluctuation - kw IPC volt voltmeter operation cluster electrical excessive generator intermittent wire #PIT3331 - (Dec 22, 2004)

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

Condition/Concern:

Some customers may comment that their voltmeter is fluctuating between 12 and 14 volts on their new 2005 model year light duty full size pickup / utility vehicle.

Recommendation/Instructions:

For 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 diagnosis 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.

Models:

(05 Chevrolet Full Size Trucks and Utilities with RVC) and (05 GMC Full Size Trucks and Utilities with RVC) and (05 Cadillac Full Size Utilities with RVC)

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.

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