possible alternator issues
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Junior User
Joined: Nov 2003
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From: oklahoma
possible alternator issues
I have a 2000 F-250 7.3 that has dual alternators. While heading to the lake the battery light came on. I always run with the headlights on so I turned them off and the charge gauge went back to up and the battery light went out. Turned lights on and the gauge went down and the battery light came on. Turned lights out and made it to lake, came back from fishing (not a bite) and the truck wont start. Jumped it got it back to camp and took batteries in to have tested both good. I am thinking it is the alternator but which one and do I need to replace both like I do the batteries.
Logistics Pro
Joined: Jun 2005
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From: AZ
You need to test the output of each alternator separately and just replace the one that is faulty, though they both may be faulty (which would mean the replacement of both). You do not need to necessarily replace both alternators like you do batteries when one goes bad.
Logistics Pro
Joined: Jun 2005
Posts: 4,243
Likes: 16
From: AZ
No dumb questions on FTE! I would suggest going by a good auto/truck electric shop (unless you have the test equipment) and have them check the alternator outputs. The voltage and amperage output of each alternator will need to be checked.
Go Bills !
Joined: Jan 2008
Posts: 2,778
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From: Buffalo, NY
Never experienced a dual alternator setup. But couldn't you just unhook one alternator at a time (via the wires) and test voltage output on the battery terminals? 14V i would say it is putting out. Then swap alternators and test again.. Would that work? Quick easier?
Also my local auto-stores test alternators, Free. (autozone/advanced/napa) But you have to remove from engine.
Also my local auto-stores test alternators, Free. (autozone/advanced/napa) But you have to remove from engine.
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Junior User
Joined: Nov 2003
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From: oklahoma
I don't know If that would work or not as I don't know how the alternators work with each other
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Senior User
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From: Jenkintown, PA
The 2 alternators are referred to a primary and secondary in the workshop manual, and the fields of each are controlled by the PCM. I haven't done much research into their operation, but I would imagine that the PCM uses some sort of program to determine how much current to expect from each. It would probably be best to have a reputable shop test them individually on the bench.
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Junior User
Joined: Nov 2003
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From: oklahoma
That is what I am going to do on Tuesday We have a local shop with a good reputation. Will post results as soon as I found out Put batteries back in today and cleaned and tightened terminals and then checked volts at battery only 12 to 13
Go Bills !
Joined: Jan 2008
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From: Buffalo, NY
Was that voltage reading with the motor running?. Your light still on after cleaning your terminals?
With mine it takes a bit for the voltage to climb. a few miles.. She will be around 11,12,13 for the longest time. At least 5 minutes. Then over 14 and stays there.
With mine it takes a bit for the voltage to climb. a few miles.. She will be around 11,12,13 for the longest time. At least 5 minutes. Then over 14 and stays there.
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Junior User
Joined: Nov 2003
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From: oklahoma
Yes. Motor running and the light went out. Drove about 45 miles home with no
Battery light but did not check voltage gauge ( mine has no numbers) shows normal for my truck which if I had to guess would be about 13 to 14
Battery light but did not check voltage gauge ( mine has no numbers) shows normal for my truck which if I had to guess would be about 13 to 14
Go Bills !
Joined: Jan 2008
Posts: 2,778
Likes: 65
From: Buffalo, NY
Mine has no number either, Dash.. I use my brake controller P3 or a standard volt meter across the terminals.. I wonder if you licked you problem with just cleaning the terminals.
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