Alternator Draining Battery
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Postmaster
Joined: Mar 2007
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From: Dunwoody, GA
Alternator Draining Battery
Recently my voltage has been low after the truck sits overnight or for longer than 10-12 hours. When I go to restart the truck it usually sits around 10-11volts. Sometimes the alternator will kick in and the voltage goes up to 13.6ish. Other times the alternator will not turn on until I rev the engine over 2500rpm. Then I'll hear the alternator whine interference noise through the speakers. Once it starts charging, it stays fine until the truck sits for a while.
I've narrowed the drain down to the alternator by removing all fuses and reading 12.6v from the negative post on the battery to the body while the positive wire is connected to the + post on the battery. When I remove the wire that goes to the alternator the voltage disappears.
The alternator is an aftermarket 6g 200amp from alternatorparts.com. This is my 2nd one from them as the 1st one took a dump less than a year after I purchased it. I do have a 1000w RMS stereo (that rarely gets used to it's full potential) and other minor electrical add ons but they are also rarely used.
From my research on the net and here, I'm leaning towards the diodes or voltage rectifier. I'd like to open up the alternator and fix it myself if possible.
Any help is greatly appreciated!
I've narrowed the drain down to the alternator by removing all fuses and reading 12.6v from the negative post on the battery to the body while the positive wire is connected to the + post on the battery. When I remove the wire that goes to the alternator the voltage disappears.
The alternator is an aftermarket 6g 200amp from alternatorparts.com. This is my 2nd one from them as the 1st one took a dump less than a year after I purchased it. I do have a 1000w RMS stereo (that rarely gets used to it's full potential) and other minor electrical add ons but they are also rarely used.
From my research on the net and here, I'm leaning towards the diodes or voltage rectifier. I'd like to open up the alternator and fix it myself if possible.
Any help is greatly appreciated!
Elder User
Joined: Sep 2007
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From: S CAL
Go ahead and open it up. The diodes should show around .7 volts in one direction and open in the opposite direction. The diodes are the rectifiers that is what they do. They rectify the voltage from AC to DC. It is the voltage regulator in these that I have not ever messed with so I cannot help you there.
Post Fiend
Joined: Jul 2005
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You mean 50 milliamps?
It takes a while to go into sleep mode --- and meanwhile, it can spike up to 300 milliamps.
Post Fiend
Joined: Oct 2009
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From: N. Fort Worth, tx
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Hotshot
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From: Middle Tn.
That is a good test that just about any dvm will work on.
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From: Middle Tn.
Elder User
Joined: Sep 2007
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From: S CAL
I would not think that the negative half cycle of an AC sine wave would do a DC battery any good, except to discharge it.
Post Fiend
Joined: Oct 2009
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From: N. Fort Worth, tx
that is fact that it will. I dont know what ill effects it really has on a battery. I test for it only with the engine running. I know a/c voltage plays havoc with eletronics that should not have them.
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Postmaster
Joined: Mar 2007
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From: Dunwoody, GA
So just stick the leads of the DMM on the battery posts while the truck is running and the alt. is charging and check for AC voltage? I'll give that a shot in the morning.
Oh and I forgot to add that I had both batteries charged and tested. Both tested good and are less than a year old.
Oh and I forgot to add that I had both batteries charged and tested. Both tested good and are less than a year old.