Question about 1992 Ford F150 SuperCab

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After having replaced both starter and alternator, the truck ran fine but the ampmeter had low readings that fluctuated. Now the battery is dead again. Will a bad battery cause the ampmeter to give low readings and how do you check the alternator output?

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  • ss5834 May 12, 2009

    Checked the small wire off the negative lead, and it appears to be good. Will take the battery in to have it checked. If I use a multimeter, to check alternator output, do I just place the multimeter leads across the battery posts or do I make contact on the wires leading to the posts?

  • ss5834 May 13, 2009

    Originally the ammeter was showing "no charge", and the battery kept dying, which is why I got a new alternator. The fluctuation began when I installed the new alternator. Re: bad voltage regulator, isn't the voltage regulator built into the alternator? If not, where is it? Thanks for your help.

  • ss5834 May 13, 2009

    Where would you place the leads on the multimeter, on the battery posts? the battery leads? One odf the three wires coming off of the alternator? I checked the poles and the reading was 12.35

  • ss5834 May 15, 2009

    Turns out the connector on the top of the alternator hadn't properly seated, resulting in an intermittent short. Thanks to everybody for their input.

  • Steeler Ed May 11, 2010

    It sounds like the new (or possibly rebuilt) alternator has a bad voltage regulator. Auto Zone can test that if you take it in. Hopefully, you still have a warranty on the replacement part.

  • Steeler Ed May 11, 2010

    IF the ampmeter is fluctuating, it sounds like a bad voltage regulator. Confirm that the voltage regulator was replaced with the alternator. Was this fluctuation happening prior to alternator replacement?

  • Greg Bernett
    Greg Bernett May 11, 2010

    What this sounds like is you have a bad ground, meaning, there would be a smaller gauge of wire off of the negatve battery lead at the battery. It is usually screwed into the fender or near it to help ground the circuit. Follow your battery leads and see where they attach to your vehicle.

    Get your battery tested for free at almost ANY automotive parts stores. They will tell you if your bad is bad, i.e., dead cells or just a bad battery that is not taking a charge....hey it's free! You can't beat free!!!



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A bad battery shouldn't give you low ammeter readings if you jump the vehicle and it stays running the alt is probably working if you have a meter to test it there should be 14-14 1/2 give or take if it is charging

Posted on May 13, 2009


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