[Shop-talk] electrical problems with truck

[John Innis]

This sounds like a bad/intermittent ground.  We had very similar issues on
a friends car and eventually trace it to the engine to frame ground strap.
The strap was loose and when it rattled just right there was a large
voltage drop and stuff stopped working.  But when we checked voltage,
everything seemed fine.  How is the volt meter in your truck grounded, to
the frame or to the motor?

On Thu, Aug 5, 2021 at 11:07 PM john niolon <jniolon at att.net> wrote:

> Took the truck (53 ford f-100) out for a drive yesterday…first time since
> the Grand Nationals (I’ve been busy) Ran great for about 30 minutes with a
> couple of stops during the ride… each time it started right and showed no
> problems. Electric fan and a/c running the whole time As I pulled out of
> one business and headed home the truck stumbled and died..almost like it
> was out of gas… ( had over a half a tank) I pulled into a business and
> tried to start it and all I got was a ‘click”. Dash Volt meter read about
> 11 volts with switch on and dropped to zero when hitting the starter.
> Waited about 10 minutes and it started right up… got it home, shut it off
> and same thing “click”.
>
> Battery has been on a battery tender full time since May and showed 13.7
> volts on VOM connected to the battery before the ride.
>
> Battery is 2 years old Everstart Maxx27 800 CCA …
>
> Davis DUI ignition (which could have quit when battery voltage got low)
>
> All cables are new with 1/0 welding cable for starting circuit and battery
> ground to frame
> engine to frame, frame to cab and frame to bed are all #4 wire to bare
> metal connection points with dialectic grease.
>
> At first glance...when running,  the volt meter on dash shows over 13
> volts so I think alternator is good
>
> did a load test with a H.F. (100 amp) load tester showed battery dropping
> to 10 volts during 10 second load... recovered to 12.
>
> Put truck up on stands and dropped battery (under cab)  checked all cables
> and connections from battery to starter including solenoid and ground
> connections.
> all tight, no corrosion on terminals and  cells full.  this truck
> finished last year and everything is new.  Starter solenoid is
> a Cole-Hersee 200 amp continuous draw solenoid.
>
> Starter is new last year and 6-7 inches away and below headers so heat
> soak isn't causing the problem
>
> Set it back down and charged it for 30 minutes at 10 amps... battery
> showed 12.9 volts..  started ok and put meter on alternator
> terminals... alternator putting out 14.5 - 14.8 volts...  varies a little
> with engine speed.... so alternator is good I think.
>
>  I did a load test again.,.. idle voltage reading 12.9 volts on two
> different fluke meters... and during the load test it dropped to 12.3 then
> recovered to 12.7...so I'm assuming the battery is good, it was just low
> before the first load test.
>
> here's an odd thing.. I have a 12 volt terminal on the right frame rail
> that powers the elec radiator fan, tilt hood motors and trinary switch
>
> 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.
>
> that's about all the detail I can give you... any ideas why it stalled and
> quit..???   and why the terminal point only reads 11.5 versus the 14.5 at
> the alternator.
>
> I'm at the wall
>
> thanks
> john
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