Help Needed on Volt Meter

Discussion in 'GM Electrical Tech' started by 71Stage1Conv, Jan 13, 2014.

  1. 71Stage1Conv

    71Stage1Conv New Member

    2009 Silverado Ext cab 4.8L

    I noticed some of the time my volt meter is reading about 12v other times 14v and at start up 14.2v. I assumed the alternator brushes were likely getting worn (90K miles), but then I read the in the manual while in the fuel economy mode it can read lower, and while running it is also normal for the reading to rise or drop?

    Some of the time I know it was not in the economy mode while reading around 12v. That doesn't seem normal to me, while running I always thought the alternator should be at 14.2. Is there a type of clutch on the alt now similar to the ac to kick on and off as needed?
    Last edited: Jan 13, 2014
  2. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Letting us know what truck and alternator combo your taking about would help us answer your question.

    GM has been using "smart" alternators for awhile. The '07 and up trucks have an alt that will adjust the output based upon load demand.
  3. 71Stage1Conv

    71Stage1Conv New Member

    Its an 09, so I guess it is the 145amp smart alt. How does it work? When it does go south, should I upgrade to the 160amp
  4. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

  5. 71Stage1Conv

    71Stage1Conv New Member

    I have added a few electrical options, plus from what I read the computer would only regulate the output anyway. All it would do is make more recharging power available only when needed without waiting energy, hence why not?

    Thanks for the napa link!
  6. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    That is all any alternator will do, they are designed to regulate the output. If the current alt is not reaching it's max output, a higher output alt will act no differently.

    But hey, it's your money.

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