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DRM796's avatar
DRM796
Explorer II
Jun 18, 2016

12v on voltmeter

Have a 2004 Silverado duramax. Driving down the road today and the voltmeter went from q4v to 12v with the battery light coming on and off. Never went below 1q and was able to drive another 110 miles. Got to the campground and after letting the truck sit for about 10 minutes it starts right up but still reads just 12v. Also noticed when ever the battery light comes on, if I get up to 2500 rpm the light will go out. Any ideas, alternator?

Thanks
Tow Vehicles
  • horton333's avatar
    horton333
    Explorer
    Jun 18, 2016
    Ditto, the residual magnetism will sometime provide a little bit of power out at higher RPMs but check the alternator or have it checked ....
  • azrving's avatar
    azrving
    Explorer
    Jun 18, 2016
    Sounds like worn alt brushes are making intermittent contact with the slip rings. In a pinch tap on it lightly and it may charge until you can replace it.
  • DRM796's avatar
    DRM796
    Explorer II
    Jun 19, 2016
    Thanks guys, found an Advance Auto Parts store 10 minutes from campground that had the alternator, replaced it and all is good.
  • Thunderbolt's avatar
    Thunderbolt
    Explorer
    Jun 19, 2016
    Yup alternator. Had that happen on my 03. The reason you made it so far may be that the alternator itself is still charging. These alternators have a a separate circuit for the gauges and warning light. This can malfunction even if the alternator is still working. That's what happened to mine. It still requires replacing the alternator though.

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