Free higher voltage charging for GM trucks

[burzendowski]

So i found some interesting information on the 05-08 general motors half tons. They have a Regulated Voltage Control (RVC) system which lowers your charging voltage to improve gas mileage. The RVC system reduces the alternators 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 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 estimated battery temperature.

heres the gm tech letter

Some owners may comment that when towing or hauling a camper/trailer that their auxiliary battery for the camper/trailer battery will not stay charged. In most cases, this concern is blamed on the new Regulated Voltage Control (RVC) system. While the new RVC system does reduce the generators 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 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 estimated battery temperature.

Recommendation/Instructions:

To correct this concern while towing or hauling a camper/trailer use the Tow/Haul feature.

Note: A second way to increase the generators targeted output voltage to 13.9-14.5 volt, is to turn on the headlights.

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.

and a link to were i found the information

http://www.gm-trucks.com/forums/lofiversion/index.php/t68427.html

[jg23]

Hmm... I'm going to have to try the tow method. I knew about the headlight method already

[burzendowski]

Hmm... I'm going to have to try the tow method. I knew about the headlight method already

Cool.... The thing about the tow mode is it doesnt use power like the headlights do which i would think is a plus. Perfect for sitting still doing demos. I did not know the headlight trick but no that i think of it my voltage was always better in the dark lol....

[RickyFriery97]

i hate the voltage crap on these trucks, finally just did dual alts with one dedicated just to the system

[burzendowski]

Thats a very good idea! I hate this charging system aswell

[PUNKYOU007]

Ok but when in tow/haul mode your transmission does not act the same as if it were not in tow/haul...on my truck it will stay in gear longer then it should if i am not actually towing. In turn your RPMs will be much higher which will kill your MPG

[burzendowski]

Ok but when in tow/haul mode your transmission does not act the same as if it were not in tow/haul...on my truck it will stay in gear longer then it should if i am not actually towing. In turn your RPMs will be much higher which will kill your MPG

That is very true, This will work well doing demos sitting still.

[dblovah51]

Ill have to try this on the hoe and see if it works for real cool info tho

[Guest DC Power Kyle]

The RVC regulators are delayed response so voltage has a hard time remaining consistent on those regulators. You will see better voltage but still expect dips in the voltage.