Question about 2001 GMC Sierra Crew Cab

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2002 GMC Sierra High Voltage

Truck show its charging at about 18 volts. When warmed up drops down to about 16.5 volts. Changed Altenator and battery and still doing the same thing. Any idea why it wont charge at 14 volts?

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Could be just a bad gauge,thak it too auto zone and have them test it while its on the truck,if it reg the same on their tester then your got a short

Posted on Mar 01, 2009


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Wasn't charging. changed battery and alternator. by the gauge it shows 14 volts but with the truck running and i unhook the battery it dies.

Not on new vehicles , you never ever pull a battery cable while it is running ! A voltage spike can take out electronic components ! That was 60's an maybe a few 70's vehicles ! That change when they started using transistors in voltage regulators an in engine modules. If it is show 14 volts it's charging ! I will send a link on how you test the charging system. How To Check Charging System EricTheCarGuy

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My sts has a good new altenator but the digital

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Won't start after battery died and recharged

Sounds like low voltage.
Get a boost from another car with a good set of cables.
Once started check voltage with booster car disconnected.
Is it around 14 volts?
If so,the truck is charging, so it may be time for a new battery.

If the voltage is at 12 or lower while running the truck is not charging.
May be time for a new alternator.

The battery should have charged enough in 1 hour to start the truck.
You may need a battery and alternator.

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have battery tested it could be the problem.

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