I’m having a issue where my alternator is only putting out about 12.8. I had it tested it said it was good but went ahead and bought a new one still having same issue, so I thought it was battery had the old one tested it tested good, but went ahead and bought a new one still same issue.
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Friday, August 21st, 2020 AT 10:42 AM
17 Replies
ASEMASTER6371
MECHANIC
52,797 POSTS
Good afternoon,
I attached a wiring diagram for you to view. Can you verify power to the alternator on the 2 wires I circled and tell me the voltage?
Did you verify power at the alternator at the 2 wires I circled?
Roy
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Friday, August 21st, 2020 AT 11:54 AM
OSBORNZAC99
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Yes 12.8.
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Friday, August 21st, 2020 AT 11:55 AM
ASEMASTER6371
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If you have power at both of those wires, the only thing left is the alternator.
You can try disconnecting the white wire. It is for the tachometer. If the cluster is the issue, then it may start charging.
Roy
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Friday, August 21st, 2020 AT 12:05 PM
OSBORNZAC99
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I tested the old alternator said it was good, but I went ahead and bought a new one and it’s still doing same thing. I guess I will disconnect that wire and see if that’s the issue and also all my fuses are good too.
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Friday, August 21st, 2020 AT 12:09 PM
ASEMASTER6371
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As long as you checked your fuses for power and not visually.
Yes, give it a try.
Roy
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Friday, August 21st, 2020 AT 12:10 PM
OSBORNZAC99
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Okay, I tried that and it’s charging at basically nothing now.
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Friday, August 21st, 2020 AT 12:15 PM
ASEMASTER6371
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Okay, back to the alternator.
What brand did you use?
Roy
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Friday, August 21st, 2020 AT 12:19 PM
OSBORNZAC99
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I originally had an O’Reilly Ultima so that’s what I went back to. I had it tested and it tested good, but I went ahead and bought a new one which I had them test straight out of box and it was good. So I threw it in my truck and still same thing is happening.
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Friday, August 21st, 2020 AT 12:20 PM
ASEMASTER6371
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How many wires on the back of the alternator?
Roy
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Friday, August 21st, 2020 AT 12:21 PM
OSBORNZAC99
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1 just the positive this alternator grounds it’s self through the brackets.
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Friday, August 21st, 2020 AT 12:22 PM
ASEMASTER6371
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Then how did you check the other wire I told you about and got 12 volts?