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alternator is not charging when fan is on

Old 05-12-2019, 11:45 PM
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Join Date: Aug 2018
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Default alternator is not charging when fan is on


i have an issue with my voltage dropping to 12.8 or even below when my fan is on and it keep killing my battery, the alternator is from 19370821 i think, its wired with one wire from the engine harness, the fan is from ford taurus which pulls 30-40 amp.

this voltage drop causing all kind of issues and its bothering me,

i dont think its the alternator as its not that old barely used less than 1000 mile on it, it been in storage most of it time mostly of because of this issue, could it be the one wire connector or maybe psi thin alternator to starter wire which is what powers the whole car or is the taurus fan draw too much amp for the alternator
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Old 05-12-2019, 11:47 PM
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Alternators have been known go bad ANY TIME from new. Yours is not above suspicion.
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Old 05-13-2019, 01:54 AM
Join Date: Jul 2006
Location: Columbus,Ga
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A bad battery will put a heavy load on a charging system. Don't overlook the basics, like clean/ tight terminals, good grounds, no missing grounds, corrosion etc....
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Old 05-16-2019, 01:05 PM
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Agree on battery health. If it is 5 years old or more, ditch it. If it has went totally dead several times, regardless of age, ditch it.

You can run a modern GM alternator to add a lot of extra oomph. I just did on my 5.3L Colorado, boosted alternator by 100amps production rating just by using a current model one, all direct from GM or Rock Auto, not a black magic shop that says high output. My alternator went from like 140 to 240 amp rating. Same size, same connectors, same everything. Plug and play. Hate to hear you not using the ride because of it. I work for the company that makes the current GM LS mass production ones, so easy for me to know what fits/works. Mine was truck accessory drive, FYI.

Last edited by FormulaBoat; 05-16-2019 at 02:16 PM.
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