Alternator Failure
Posting Guru
Joined: Dec 2006
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From: Kansas City/Breckenridge
Pretty common. Mine quit at 60k. Make sure your next one has a lifetime warranty
It's usually caused by one of your batteries failing. Make sure you check and replace both of them.
It's usually caused by one of your batteries failing. Make sure you check and replace both of them.
Freshman User
Joined: Feb 2004
Posts: 27
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From: Texas
I lost my on my truck recently at ~43K miles. Both batteries went at the same time. Replace all 3 and no more problems.
Post Fiend
Joined: Jul 2005
Posts: 6,127
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Check the power circuit to the field winding --- that is powered by the battery.
Often, it is just a bad contact there --- killing alternator output --- then killing battery.
Nearly no one bench test alternators after they are removed.
If it is this fault, the alternators will bench fine --- bet a lot of perfectly good alternators are replaced because of this.
BTW, bench the NEW alternator before you install it... smiles...
You might be surprised.. unpleasantly.
Often, it is just a bad contact there --- killing alternator output --- then killing battery.
Nearly no one bench test alternators after they are removed.
If it is this fault, the alternators will bench fine --- bet a lot of perfectly good alternators are replaced because of this.
BTW, bench the NEW alternator before you install it... smiles...
You might be surprised.. unpleasantly.
Freshman User
Joined: Feb 2004
Posts: 27
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From: Texas
One other note, when I took the alternator off, I took it to the normal auto supply houses and had it tested. Three different ones to be exact and each time the alternator tested "good". I checked all the wiring and the ground and everything was good. I decided to go with just new batteries due to the alt. checking out good. Put the new batteries and old alternator back on the truck and drove it to a funeral about 3 hours away. All was good on the way over but on the way back the battery light came back on. Got home and checked DC power on the batteries with the truck running and the voltage was only 12.1 volts. I think it is suppose to be ~14V so I decided to go ahead and replace the alternator and that has fixed the problem. I doubt seriously that the alternator failed on that trip.
Just adding some experience.
Just adding some experience.
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Post Fiend
Joined: Jul 2005
Posts: 6,127
Likes: 6
One other note, when I took the alternator off, I took it to the normal auto supply houses and had it tested. Three different ones to be exact and each time the alternator tested "good". I checked all the wiring and the ground and everything was good. I decided to go with just new batteries due to the alt. checking out good. Put the new batteries and old alternator back on the truck and drove it to a funeral about 3 hours away. All was good on the way over but on the way back the battery light came back on. Got home and checked DC power on the batteries with the truck running and the voltage was only 12.1 volts. I think it is suppose to be ~14V so I decided to go ahead and replace the alternator and that has fixed the problem. I doubt seriously that the alternator failed on that trip.
Just adding some experience.
Just adding some experience.
Bad contact at the field winding connection would have exactly the same symptom.
And your act of R&R of alternator could have just tweaked the connector enough to give a good contact.
Note: the other possibility is the wiring went bad internally inside the housing!
See my wiring fault page for details.
Freshman User
Joined: Feb 2004
Posts: 27
Likes: 0
From: Texas
Bad contact at the field winding connection would have exactly the same symptom.
And your act of R&R of alternator could have just tweaked the connector enough to give a good contact.
Note: the other possibility is the wiring went bad internally inside the housing!
See my wiring fault page for details.
And your act of R&R of alternator could have just tweaked the connector enough to give a good contact.
Note: the other possibility is the wiring went bad internally inside the housing!
See my wiring fault page for details.
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