Alt. Not Charging
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Freshman User
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From: oregon
Alt. Not Charging
i've replaced and double checked the altinator, voltage regulator, starter, starter silinoid, battery, and the little three prong thing by the silinoid. and my altinator still isn't charging. any ideas.
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From: Virginia
What year vehicle are you working on? What are the symptoms? Do you have a voltmeter?
Taking a wild guess, I would say starting at the alternator, follow the large output wire all the way up to the starter relay. Somewhere along the way you may find a rubber piece in the wire. This is a fusible link, and may be burned out.
Taking a wild guess, I would say starting at the alternator, follow the large output wire all the way up to the starter relay. Somewhere along the way you may find a rubber piece in the wire. This is a fusible link, and may be burned out.
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From: oregon
it's a 73 ford f250 4x4 crew cab with a 300 six. everything is factory, so there isn't a bunch of cut wires everywhere. the ground from the battery to the block looks good, is there another strap i need to look at.
i followed that wire up and i cut out the fuseable link and replaced with a 20 amp fuse. when i start the truck it runs but when i pull the fuse out it dies so i know its good. is 20 amp fuse there big enough?
with truck off i get 12.9 volts out of battery with no load or drain on it. with truck running i get 12.6 at battery and the same off the back of alt.
i followed that wire up and i cut out the fuseable link and replaced with a 20 amp fuse. when i start the truck it runs but when i pull the fuse out it dies so i know its good. is 20 amp fuse there big enough?
with truck off i get 12.9 volts out of battery with no load or drain on it. with truck running i get 12.6 at battery and the same off the back of alt.
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With the voltages you describe the alternator is not putting out any juice. The alternator or the regulator could be bad, or you could have bad wiring between the regulator and the alternator. It appears you have checked or replaced everything else so it is time to start checking the wiring with an ohmmeter or a test light. The wiring diagram will help with this. One of the books, Haynes or Clymers, don't remember which and they are at home, has a wiring diagram in the back.
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From: Virginia
i followed that wire up and i cut out the fuseable link and replaced with a 20 amp fuse. when i start the truck it runs but when i pull the fuse out it dies so i know its good. is 20 amp fuse there big enough?
Take the + battery cable off the battery. Take your voltmeter and put it on rx1 scale. Touch the two meter leads together, and you should get close to zero ohms. Then take one of the meter leads and put it on the disconnected battery + cable end, and put the other meter lead on the large output post on the back of the alternator. You should get close to zero ohms. This will tell you the output wire is ok.
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From: oregon
I went to the junk yard and pulled out the wire loom between the alt and silinoid and from the regulator up. the one i pulled out has three fuseable links on the battery side of the silinoid and my truck only has one. they are both 73 f250. mine has a 300 six and the other has a 390?? why would mine only have one? i found no evidance of cut wires.
thanks.
thanks.
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From: Virginia
I don't have an answer for that, but most of them have more than one. You are getting a little bit early in your year truck and what I am familiar with. I don't know when they started using fusible links, but the old 60's vehicles didn't have anything for protection.
The most common reason they burn out is someone changes the alternator and forgets to take the battery + cable off first.
The most common reason they burn out is someone changes the alternator and forgets to take the battery + cable off first.
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From: oregon
update, first thanks for the help all.
during the invistigation i found that the guy that put the davis unified ignition in left the hot coil wire from the back of the key switch loose under the hood. since you don't need that wire anymore it just hung there. well somehow it must have got a ground and burned up the wire in the harness. in the process it melted other wires and now i need to go pull the rest of the wireing harness out of the junkyard 73 before someone beats me to it.
thanks.
during the invistigation i found that the guy that put the davis unified ignition in left the hot coil wire from the back of the key switch loose under the hood. since you don't need that wire anymore it just hung there. well somehow it must have got a ground and burned up the wire in the harness. in the process it melted other wires and now i need to go pull the rest of the wireing harness out of the junkyard 73 before someone beats me to it.
thanks.