Battery voltage gauge seems inconsistant

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by jeremyc, Sep 26, 2012.

  1. jeremyc

    jeremyc New Member

    Hey all. I am new to this site and recently purchased a 2012 Silverado Z-71 with the All Star Edition. I noticed my battery gauge needle is moving more than I have ever seen one move before. It appears the needle fluctuates between 12 and 15 or volts. The battery gauges on most vehicles I have owned stays around 13 to 14 volts and doesn't move much unless something that consumes a lot of power is turned on. Mine does this with nothing additional running on the truck other than the radio and a/c.

    This morning the needle was about 1 volt below (13 volts) the middle mark (14 volts) on the gauge. I noticed it, turned the truck off, restarted the truck and the needle went about 1 volt above (15 volts) the middle mark of 14 volts.

    Has anyone else noticed this in their trucks?

    BTW, this won't be my first post, gain info, then bail out. Someone pulled out in front of me and totaled my 84 GMC truck. I was/am very active in another forum that was started primarily for older trucks. Nonetheless, that truck is gone and I am looking for new forums to get involved with that have lots of info for newer trucks.

  2. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Jeremy if you look in the owners manual it can explain the system much better than I can but your 2012 truck has a variable charging system that only produces the current needed to operate electrical systems on at any one time and perform a trickle charge/maintenance charge on the battery.
    If I remember the section your looking for will either be labled "Charging system", or it might be under the gauge description.
  3. jeremyc

    jeremyc New Member

    Thank you for your response! I didn't read the manual word for word from cover to cover, but I did spend about 15-20 minutes skimming through it. I just now found the section that discusses this on page 5-18.
  4. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    My 05 does the same thing with a new alternator and battery. In the city it is around 14 volts, when I get on the highway it drops to 11-12 volts. If I put all 4 windows up at the same time the lights dim for a second and then the voltage goes up to 14-15 volts. As soon as I let go of the buttons it drops back to 11-12
    Last edited: Oct 2, 2012
  5. j cat

    j cat Epic Member 5+ Years 1000 Posts

    the guage on my 2000 silverado and the 2002 stays at the 14 volt point with the engine running and very rarely moves off this reading.

    when the alternator regulator started to go the voltage would drop to just above 12 volts then jump back to 14volts.

    Using a dc volt meter measure the alternator output voltage, compare with the dash guage.

    load up the electrical system all on see if it holds or drops.

    just because its new does not mean the battery is good, or the connections to it are in need of cleaning and securing.

    could also be a defective alternator,dash guage, or wiring.
  6. CanSkan

    CanSkan New Member

    Both my 2012 and my buddy's 2012 do the same thing.... dealer explained to him that it is a fuel saving feature.... alternator only runs when required then shuts down to save load on vehicle and thus better gas mileage.... hope their right.
  7. j cat

    j cat Epic Member 5+ Years 1000 Posts

    the load on my 2000 SIL is about 66AMPS with the engine running . If the alternator cycles on and off the Battery is going to suffer.

    I guess it is possible the alternator output is throttled to limit its output and reduce load on the engine. that would not save you much on power/MPG.

    If true this would be something to check out.
  8. WorthFlorida

    WorthFlorida Rockstar 4 Years 100 Posts

    My 2012, 1500 5.3l with less than 1K miles also does this. The seond day of ownership the battery died becuse it wouldn't hold a charge and was replaced by the dealer. I then noticed that the voltage at times would be around 13 volts. After restarting the engine it would go to the 15 volt area. The manual is 584 owner manual size pages in pdf format. About 240 pages in standard 8.5'x11" and I havn't had time to read all of it. I'm glad I joined this forum for it saved me a trip to the dealer.
  9. j cat

    j cat Epic Member 5+ Years 1000 Posts

    with your dash guage readings it is quite possible they have a bad batch of alternators. high voltage will also damage a battery as well as the electronic devices/PCM.

    15volts would be if it was zero deg F air temp on a cold start. this woulld only be at that amount for a short time. the higher voltage heats up the battery quicker. a battery must be warm to accept a charge.
  10. the phantom

    the phantom Epic Member 5+ Years ROTM Winner 1000 Posts

    I also have read (I believe in the owners manual) that the charging system does vary. I have noticed that my 2011 does do this so what you are describing is normal. I am sure that there are not a bad batch of alternators as someone has previously suggested.

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