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I replaced a brand new battery and the alternator but my scan tool says the charging voltage is under acceptable limit?

BEFORE testing, the voltage is about 14.2V at idle.

However, AFTER testing (according to my scan instructions), it says the charging voltage is under acceptable limit.

What else could be wrong? Obviously, can't be the battery or the alternator since they both are brand new.

Here is the video:

https://www.youtube.com/watch?v=ypa212sqvtk

Youtube thumbnail

Update:

It was a little bit hard to read but it says 12.93V at the end of the video

Update 2:

and btw, it's 2013 Honda Civic EX 

11 Answers

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  • Dan
    Lv 5
    2 months ago
    Favorite Answer

    Absolutely nothing wrong! Your only problem is your generic scantool doesn't know how Honda charging systems work, they are much different. Over the years I have seen thousands of dollars go down the drain as inexperienced techs did diagnostic tests just like this and replaced parts for no reason.

    Honda's have load a detection module as well as a standard regulator. The load detection module shuts the alternator RIGHT OFF! - if it feels like it. In other words, you'll see battery voltage while the engine is running if the battery has a good charge on it and it's not heavily loaded - Completely normal for a Honda!

    Read this:

    https://cdn.shopify.com/s/files/1/0245/2167/0752/f...

  • Anonymous
    2 months ago

    I have a standard Voltage meter and one I can fix to the Battery and tape to the Bonnet so I can start the car drive the car and monitor the Voltage

     I was told need a new Alternator or new Battery when all I needed was a Voltage Regulator which I changed for one I knew works charging at 41.2 volts and drops to about 11 Volts on Starting

    My Volt meter has been in use for 40 years so good i purchased another one from Ebay one in the car one in the shed

    your tester might need Calibrating

  • 2 months ago

    Check the charging system fuse. If that $1 fuse blows, charge cannot get from the alternator to the battery. With the engine running, check voltage across the battery terminals to see if the 14.2 volts shows up there.

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  • hart
    Lv 6
    2 months ago

    bay a new scan tool

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  • 2 months ago

    How long ago did you change the battery and how long has it ran since? At an Idle the voltage is low, but was still charging. Anything over 12.8 is charging, but if the battery is fully charged it should say over 13 at an idle. New batteries are rarely fully charged and can take 30 min or more to become fully charged.  I would recommend either charging with a battery charger, or going for a drive then do your test again. 

    Source(s): 20+ years of Heavy/any equipment repair
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  • Scott
    Lv 7
    2 months ago

    No, you can't automatically assume it can't be the battery or the alternator. I've had bad alternators right out of the box.

    • don_sv_az
      Lv 7
      2 months agoReport

      and I've had batteries fail within 15 days.

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  • 2 months ago

    If you installed a cheap after market alternator rebuilt alternator try a factory alternator. The PCM that controls the alternator is not getting the proper readings from the after market alternator. This happens all the time on Honda's.

    Source(s): Mitsubishi Master Tech
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  • Barry
    Lv 5
    2 months ago

    The charging volts are spot on. Forget what your scanner says.

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  • 2 months ago

    14.2 volts is fine.  Carry on. 

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  • 2 months ago

    Trust you old school voltmeter or multimeter. Scan tools are just a good way to point you toward a list of possible problems then you use your multimeter to check voltage and run Ohms tests to determine which part is bad or broken.

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