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free_radical's avatar
free_radical
Explorer
Dec 16, 2013

Starting battery question

I dont have electrical gauge in the dash,
so have bought small Gauge that plugs into the 12V outlet and displays the electric current quite accurately,along with Yellow,Green and Red lights and bar showing battery state of charge..
The truck runs and starts perfect in any weather,
however the Gauge reads -11.99 and Red light on some cold mornings siting overnight,seems kinda low imo..
turns to Green and reads 14-15+ as soon as it starts,
then fluctuates up and down stays mostly Green and Yellow with normal Voltage,
though sometimes even at high speed the light stays Red and reads low Volts again.

Does the Alternator stops charging at some speeds and why,or is all this normal?

10 Replies

  • free_radical's avatar
    free_radical
    Explorer
    Dec 17, 2013
    MEXICOWANDERER wrote:
    One of two things should say hello to the garbage pail.
    a) Gauge
    b) Alternator
    This needs to be checked out to find which one is at fault.

    Since it always starts and runs great I suspect the Gauge is not all that acurate,
    battery is only about a year old
    I will check the battery charge in the morning with a multimeter as someone suggested.

    thank you all for help..
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Dec 17, 2013
    One of two things should say hello to the garbage pail.

    a) Gauge

    b) Alternator

    This needs to be checked out to find which one is at fault.
  • Canadian_Rainbi's avatar
    Canadian_Rainbi
    Explorer
    Dec 17, 2013
    free radical wrote:
    I dont have electrical gauge in the dash, so have bought small Gauge that plugs into the 12V outlet and displays the electric current quite accurately,
    along with Yellow,Green and Red lights and bar showing battery state of charge..
    The truck runs and starts perfect in any weather,
    however the Gauge reads -11.99 and Red light on some cold mornings siting overnight,seems kinda low imo..
    turns to Green and reads 14-15+ as soon as it starts,
    then fluctuates up and down stays mostly Green and Yellow with normal Voltage,
    though sometimes even at high speed the light stays Red and reads low Volts again.

    Does the Alternator stops charging at some speeds and why,or is all this normal?


    I'm not trying to pedantic, but this gauge does not display electric current (measured in Amperes) but voltage (AKA Electro Motive Force) measured in Volts.

    You must be clear on the difference between voltage and current if you are going to use a multimeter as Shadow Catcher recommended. Measuring Volts on the Current (Amps) setting and vice versa will destroy the meter, or at least that function.

    And Shadow Catcher is correct. Get and use a multimeter It can clarify a lot of puzzling situations.
  • Hank_MI's avatar
    Hank_MI
    Explorer
    Dec 17, 2013
    When your gauge reads 11.99v I would check battery voltage with a good VOM. I don't think your battery is really down to 11.99v. That's basically a dead battery, 25% charge and unlikely to start your truck.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Dec 17, 2013
    Alternator output may drop below engine needs when engine is at full idle.

    From what you post you may (or may not) have a battery problem. Further testing and/or a better tester are indicated.
  • Shadow_Catcher's avatar
    Shadow_Catcher
    Explorer
    Dec 17, 2013
    A good quality VOM/Multimeter is your friend. What is the battery voltage at rest after a night? You still have some load but it should be as indicated above 12V, after starting you should see 14+ tested at the battery. Places like Auto Zone will test your battery and alternator for free.
  • westend's avatar
    westend
    Explorer
    Dec 17, 2013
    It may be that your battery is very cold when the gauge is reading at it's lowest and the gauge is not completely accurate. The gauge seems to be following normal charging sequences but is reading too low. Unless you have a bad cell in the battery, the gauge should never read below 12.4-5 when the engine is running.
  • red31's avatar
    red31
    Explorer
    Dec 17, 2013
    I have a similar voltage gauge and just because it is digital to two places, I do not consider it quite accurate.

    12v on a cold morning is too low, original battery?

    When I plug in my voltmeter and ride down the road ('07 chevy), it reads 12.5v to 14.7v as the RVC does it thing. It cycles ever 30min or so after it has charged the battery from being used to start the vehicle. It has a mind of its own. Seems to provide no alternator current at times.

    http://www.archivedsites.com/TECH_CONNECT_new/English/2005/TechConnect03%20MayJune05%20Final.pdf

    Use tow/haul mode to override or turn on the headlights! The battery current sensor will tell the computer to up the voltage.

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