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Old 05-28-2010, 09:38 AM   #1
dmancuso
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Unhappy Still only 12 volts

Still showing 12 volts replaced battery, alternator, starter and battery cables,
getting 12V no matter what idle or accelaration. Changed the fused ling at starter, guess i', just running off the battery just a matter of time. Whwn I purchased the truck it had a differant engine could it be that it it's only should be at 12 volts? was there at one time older trucks ran at only 12 volts?
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Old 05-28-2010, 10:02 AM   #2
FLEET72
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Re: Still only 12 volts

Are you going by the gauge in the dash or a hand held voltmeter?
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Old 05-28-2010, 10:27 AM   #3
dmancuso
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Re: Still only 12 volts

gauge in the dash and aftermarket autometer gauge .
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Old 05-28-2010, 12:10 PM   #4
FLEET72
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Re: Still only 12 volts

Measure the voltage at the battery. With the engine off, it should be 12.7 volts or more. With the engine running it should be 13.5 volts or more. If these measurements are good, the wiring connections between the battery and your instrument panel need to be addressed. Poor ground connections are a common cause of low readings.
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Old 06-03-2010, 12:18 AM   #5
datguysaL
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Re: Still only 12 volts

check your ground cables and straps.
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Old 06-03-2010, 07:34 AM   #6
James McClure
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Re: Still only 12 volts

Mancuso, Disconnect the alternator. With a test light see if all 3 wires are hot with the key ON. They all should show power. The brown wire should be dimmer than the others. If any of the wires don't show power you found the problem, just backtrack till you find the open. Next hook it back up and start the eng and test voltage right at the alt output lug. As stated above it should be above 13 volts. If not, the alt is bad. I strongly suspect a wireing issue. There are 3 or 4 fuse links in our trucks, check them all. jim
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