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Re: [Shop-talk] electrical problems with truck

To: shop-talk@autox.team.net
Subject: Re: [Shop-talk] electrical problems with truck
From: Jimmie Mayfield <mayfield+shoptalk@sackheads.org>
Date: Fri, 6 Aug 2021 09:18:11 -0400
Delivered-to: mharc@autox.team.net
Delivered-to: shop-talk@autox.team.net
References: <1UZ4YZ76KH.7AHYM3yYtnG.ref@johns-desktop> <1UZ4YZ76KH.7AHYM3yYtnG@johns-desktop>
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On 8/5/21 10:33, john niolon wrote:
> with the a/c on, headlights on and elec radiator fan running (as much 
> load as I can put on it)... the alternator o/p at 14.5 volts, the 
> voltage at the terminal on rail reads 11.5 volts.  The terminal is 4' 
> from battery and fed with #4 stranded wire.

I think this might be the smoking gun.  The voltage you're seeing at 
that terminal with the engine 'on' is roughly what I would expect to see 
if you were powering things only with your battery.  But let's check 
some things before I jump to conclusions...

1. Double-check the electrical path between this terminal and the 
battery/alternator to make sure there's no corrosion that might increase 
resistance.

2. What's the voltage at the terminal with those accessories 'on' but 
the engine 'off' ?

3. How big is the alternator?  Do you know offhand what its rated output 
is at various engine RPMs (some aftermarket manufacturers provide this 
info).  Sometimes folks with big audio systems will run into 
dead-battery problems after installing a high-output alternator because 
the new alternator's 'preferred' RPMs don't match up with the owner's 
typical driving style.

-- J




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    <div class="moz-cite-prefix">On 8/5/21 10:33, john niolon wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:1UZ4YZ76KH.7AHYM3yYtnG@johns-desktop"><span
        style="FONT-SIZE: 13px; FONT-FAMILY: Verdana, geneva, lucida,
        &quot;lucida grande&quot;, arial, helvetica, sans-serif;
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        font-variant-caps: normal; -webkit-text-stroke-width: 0px;
        text-decoration-thickness: initial; text-decoration-style:
        initial; text-decoration-color: initial">with the a/c on,
        headlights on and elec radiator fan running (as much load as I
        can put on it)... the alternator o/p at 14.5 volts, the voltage
        at the terminal on rail reads 11.5 volts.  The terminal is 4'
        from battery and fed with #4 stranded wire.</span></blockquote>
    <p>I think this might be the smoking gun.  The voltage you're seeing
      at that terminal with the engine 'on' is roughly what I would
      expect to see if you were powering things only
      with your battery.  But let's check some things before I jump to
      conclusions...</p>
    <p>1. Double-check the electrical path between this terminal and the
      battery/alternator to make sure there's no corrosion that might
      increase resistance.</p>
    <p>2. What's the voltage at the terminal with those accessories 'on'
      but the engine 'off' ?</p>
    <p>3. How big is the alternator?  Do you know offhand what its rated
      output is at various engine RPMs (some aftermarket manufacturers
      provide this info).  Sometimes folks with big audio systems will
      run into dead-battery problems after installing a high-output
      alternator because the new alternator's 'preferred' RPMs don't
      match up with the owner's typical driving style.<br>
    </p>
    <p>-- J</p>
    <p><br>
    </p>
    <p><br>
    </p>
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