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1967 - 1972 F-100 & Larger F-Series Trucks Discuss the Bumpsides Ford Truck

Troubleshooting

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Old Jan 26, 2012 | 02:43 PM
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Stalknappen's Avatar
Stalknappen
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Troubleshooting

Hello Ford enthusiasts! At first i have to excuse my english but i hope you guys will understand =)

I have a problem with my Ford F100 from year 68 with a 390 and C-6 trany. Now to the case, sometimes it runs great but usually when it gets warm it starts to "missfire" and have a rough idle and runs bad, sometimes it even stalls. If i measuring on the battery when it goes bad, the volts jumping from 13 to sometimes 20V. If I move the throttel a littlebit it starts to charge around 13V. I had checked the basic things and replaced the rotor,distriburator cap,ignitionwires,condenser and contact set. So now i hope that someone out there can give me a tip whats up with my car

Best regards from Sweden!
 
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Old Jan 26, 2012 | 04:39 PM
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You should have 12v across the batt terminals with engine off, and 13.5 to 14v across the terminals when the truck is idling. Anything more means your charging system is whack. Sounds like you need to have the alternator tested, and maybe replace it and the voltage regulaor, if it looks like it is stock.
 
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Old Jan 26, 2012 | 06:03 PM
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I would replace the voltage regulator first. I have seen with a broken aftermarket amp gauge the voltage regulator was not able to read any voltage through the gauge and caused the alternator to put out like 25 volts.
 
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Old Jan 27, 2012 | 07:00 AM
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troubleshooting

Sir, Be sure to look at the grounding from battery to engine to body and frame, this can also cause voltage spikes. Kenny,
 
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Old Jan 27, 2012 | 08:16 AM
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NumberDummy
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1965/81: Alternator voltage regulators have points, get stuck. Peeps rap on the covers with knuckles, screw driver handles, anything available to unstick points. So if cover has dings in it, this has occurred before.

1982: FoMoCo replaced the point type regulator with an electronic solid state version. Has a flat cover with MOTORCRAFT marked on the diagonal.

The original wiring harness is used with this regulator, no mods are necessary to install it.
 
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Old Jan 28, 2012 | 05:33 AM
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Thanks for all answers, i will try to change the voltage regulator then and see if it gets better.
 
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