Alternator Output Too High?
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Elder User
Joined: Mar 2008
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From: Sandy Hook, CT
Alternator Output Too High?
Went outside to start my 96 F150, found the battery dead. Charged it up, started right up. Next morning, same thing...had the alternator bench tested at Advance Auto and its putting out 16volts. Does this warrant replacement? What would this have done to the battery? Thanks in advance!
Roger
Roger
Fleet Mechanic
Joined: Jan 2009
Posts: 1,964
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From: Fort Worth
The alternator is supposed to be higher than battery voltage, but usually around 13.5 to 14.5ish volts so that the battery is charged. The voltage regulator is what maintains that voltage window. If it goes much higher than that, it can cook the battery. My guess is that your voltage regulator wasn't working properly which let the alternator's high output create too large of a current to the battery, which overcharged the battery and killed it.
Edit to add a second thought...
It could also be that the VR is working properly and it's not letting that flow of current to the battery because the alternator's output voltage is over what the VR is set to regulate it at, so it's just not charging. Either way, it's an alternator/VR problem.
Edit to add a second thought...
It could also be that the VR is working properly and it's not letting that flow of current to the battery because the alternator's output voltage is over what the VR is set to regulate it at, so it's just not charging. Either way, it's an alternator/VR problem.
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