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Voltage gauge changing

Coolmaker

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Coolmaker Enthusiast

Coolmaker

Posted
Posted

Was out yesterday putting some miles on the new 2012 Sierra Slt w/ 6.2.. As always with a new vehicle I watch the gauges like a hawk. After about 30 miles of continuous driving the voltage gauge came down to 12 volts from about 14.5..

 

Pulled over, shut the engine off, restarted it and it went back to 14.5 for about 25-30 miles again and then went to 12 volts on the gauge. No light came on though that showed the alternator was not charging. This time I just kept driving and after 20-25 miles the voltage gauge slowly came back up to 14.5 volts and remained there until i got home.

 

This is the third time it has done this. Is there something else in the new systems that regulate the voltage other than the alternator?

 

All wires on the alternator and battery are tight and all plugs are firmly seated....

 

Anyone have any ideas, other than take it to the dealer and let them test it?

Patch6713 Enthusiast

Patch6713

Posted
Posted

I read that it is an attempt to increase fuel mileage by lowering the amount of that the alternator is charging. I can't remember where I read it but it was after my father made a trip in his new truck and commented to me that the voltage was low on the highway. Looked it up and that's what it said.

CRTurboGuy Enthusiast

CRTurboGuy

Posted
Posted

Glad I'm not the only one. I noticed the same thing over Christmas on a trip to MN that it would drop down at times, figured it was probably something related to fuel economy, glad to know that it's not broke.

 

--JOsh

Coolmaker Enthusiast

Coolmaker

Posted
  • Author
Posted

Thanks for the answers. I really did not get to upset, because the "no charge" light never came on....

Wolfmanjohn Enthusiast

Wolfmanjohn

Posted
Posted

The Helm manual states that there are ~ 6 different charging levels/voltages/states that can be commanded by the PCM depending on electrical and battery requirements and demand. As written above, it's normal to see what you do at the voltmeter.

 

Enjoy your 6.2!

Coolmaker Enthusiast

Coolmaker

Posted
  • Author
Posted
It's explained in the owners manual. Yuh know, that thing in the glove compartment!

 

That would be cool if one can read..

tesnoboy Enthusiast

tesnoboy

Posted
Posted

So how exactly does it save fuel? Does the alternator have a clutch like the AC compressor now? Freewheels when not needed?

travis73 Enthusiast

travis73

Posted
Posted

I also noticed anytime you hit the tow haul button the alternator starts charging again,It's a smart system,worried me at first too,perfectly normal.

dewfpo Senior Enthusiast

dewfpo

Posted
Posted

So how exactly does it save fuel? Does the alternator have a clutch like the AC compressor now? Freewheels when not needed?

 

 

If the alternator is not charging then it is not creating a lot of resistance, this reduces the drag on the serpentine belt which in turn, uses less horsepower. In the old days (70's and before), before the days of ECM controlled idle speeds, you could turn on your headlights, heater and windshield wipers, and you could hear the alternator strain on the fan belt and you could see the idle speed drop as the load on the alternator was increased. It takes HP to run anything on a vehicle.

 

DEWFPO

c4cruiser Enthusiast

c4cruiser

Posted
Posted

I also noticed anytime you hit the tow haul button the alternator starts charging again,It's a smart system,worried me at first too,perfectly normal.

 

Not only will the alternator start to charge again, but the amerage output of the alternator increases over its normal rate. The idea is when you may be towing a trailer; the additional output is a help to charge a battery on the trailer.

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