Question about GMC Sierra 1500
Check that the alternator and charging circuit is actually working. You can do this with a voltmeter across the battery terminals. Check the value with the ignition off - you should see 12.1 and 12.5 volts. Then start the engine and leave it on idle - you should see between 13.8 to 14.2 volts. Watch the voltmeter as the gas is pressed down. With the engine revving around 2000 rpm the voltmeter value should increase up to something like 14 to 14.2 V but not increase any further with an increase of engine revs. If you see voltages of 14.5V or above then the voltage regulator needs replacing.
Note that if you constantly see voltages of 12V or less with the engine switched off then the battery should be replaced as it will not hold charge and gradually drain down as you are experiencing to a point where it will not turn the car engine.
If you don’t see any increase in battery voltage, or the battery voltage falls, when the engine is switched on then either the alternator or the voltage regulator need to be replaced.
Posted on Nov 19, 2009
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Posted on Jan 02, 2017
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