Alternator draining my battery

[mtnman210]

When I went to start the truck this morning it started as if the battery were going dead. Once I was driving I noticed I had only about 10volts and it wasn't charging.
So I started to trace the problem and found that my alternator has power going in and coming out even with the ignition off. This is obviously the source of my drain but why would the alternator be getting constant voltage? what can I look at before I go out and replace the alternator?

 

[longbedder]

A shorted diode in there can cause the stator windings to stay energized, or a bad regulator can cause the field to stay energized.

 

[chulisohombre]

the diode is bad.its allowing electricity to flow both ways instead of just output to the battery.if you dont know how to replace electronic parts it would be easier to replace the alternater.you would have to rebuild it to fix the problem.if its only putting out 10 volts it is not charging correctly either way.from the sounds of it you may be better off replacing it.

 

[djsblaze]

Can I chime in? Similar problem. Truck starts slow, volts show 12 under throttle, 9-10 when slowing down or idling. Tested it at OReillys and they say alternator is good. Batteries test good too. No stereo, just a winch that has not been used anytime recently, so I don't think its related. 2 optima redtops. I'm no genius, and I'm stumped...thanks

 

[readymix]

What volt meter are you going off of?
Hopefully not the one in your dash.

 

[K5dreamer]

djsblazer - time to check the starter motor.

 

[dyeager535]

As an aside, "rebuilding" the alternator is one of the easiest things you can possibly do...you've got to remove it anyways.

Don't know what the kits go for, but last time I did it was something like $20. Bought a new bearing for I think $5. Done it on enough now that it takes about 15 minutes to replace the parts in it.

I'm guessing for the most part "new" parts store alternators are cheap, I doubt they do anything more than clean them, and put the exact same parts kits in them.

 

[mtnman210]

no I'm not going by the gauge in the dash I'm using my hand held volt meter so I should be getting an accurate measurement.