Bad Alternator?
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Joined: Nov 2005
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Bad Alternator?
I have a '97 F350 with the 460ci V8. Recently, my truck began having a weak or dead battery. It won't start after sitting for a day or so. Sometimes it is a couple of days, other times it is only overnight. Battery is weak and won't crank the motor or completely dead. But truck will jump start just fine.
Battery was only showing 11 volts, had it tested at Autozone and they said it was fine. Charged it up and the truck started fine.
Checked voltage across the battery terminals while the engine was running....showed 13 volts....so should be charging the battery although i thought it would typically register closer to 15 volts. Drove the truck for awhile and notice the voltmeter on the dash dropped some. Tested across the battery terminals while running again....a little over 12 volts.
Turned truck off, battery showed 12 volts...for a short time...then dropped back down to 11 volts.
Sounds to me like my alternator is going bad and may be draining the battery while it sits overnight. Anyway to test my theory?
Electrical problems are not my strength! In fact, I despise them since there are so many potential sources for the problem!
Battery was only showing 11 volts, had it tested at Autozone and they said it was fine. Charged it up and the truck started fine.
Checked voltage across the battery terminals while the engine was running....showed 13 volts....so should be charging the battery although i thought it would typically register closer to 15 volts. Drove the truck for awhile and notice the voltmeter on the dash dropped some. Tested across the battery terminals while running again....a little over 12 volts.
Turned truck off, battery showed 12 volts...for a short time...then dropped back down to 11 volts.
Sounds to me like my alternator is going bad and may be draining the battery while it sits overnight. Anyway to test my theory?
Electrical problems are not my strength! In fact, I despise them since there are so many potential sources for the problem!
Post Fiend
Joined: Nov 2008
Posts: 23,849
Likes: 20
From: McKenzie River
Leave it to autozone to screw up a battery test, sounds like battery is weak. It should still read 12.2 to 12.8 at rest..............But it also sounds as if your alt. is also weak, it should be charging at about 13.8/14.0 volts........Get ready to spend a little $$$.
