What Size Alternator Can You Install?

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Rob & Cathy

Re: What Size Alternator Can You Install?

Post by Rob & Cathy »

True, but it sounds like it stays there no matter what the duration.

Rob
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bigbunkhouse
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Cardinal Owners: 2007 362BHS
Location: Massachusetts North Reading

Re: What Size Alternator Can You Install?

Post by bigbunkhouse »

Found this little piece of info,
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 Silverado, Silverado Classic,

2005-2008 GMC Sierra, Sierra Classic,

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.
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Rob & Cathy

Re: What Size Alternator Can You Install?

Post by Rob & Cathy »

It sounds like anything between 12.6vdc and 15.5vdc is normal for a 2005-2008 GM pickup. :?

Rob
rlhedlund

Re: What Size Alternator Can You Install?

Post by rlhedlund »

Makes sense now. When I leave for work, it is 0'dark thirty, so the headlights are on. Hence the higher voltage output. IU also have fog and after market driving lights on.

This weekend, I left the house when it was light and the voltage was on 13.8 with no headlights.

I did notice today though, that even with the startup voltage at 11.8, the accessory outlet was still powered up. ??? Any info on that?
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