1991 F150 "Battery Light" comes on

1991 Ford F150 6 CYL New Alternator (Old one was probably OK) 1 year old battery After about 10 Minutes either running at Idle or at 35MPH the Battery Light
comes on and stays on Measured the voltage at the battery 14.5 running 12.6 turned off.
Anyone have a guess?
Thank you in Advance
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Probably the resistor at the battery light.
carpool wrote:

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Does the alternator feel hot to the touch? Is the measured voltage consistent? Does the light go off at speeds above 35MPH? How long has this been happening? Are all the wires and connections in good condition? Is the belt tight?
Perhaps a diode or triode, or insulation is failing when the alternator gets hot.
As you may know "shorted" diode can produce the correct voltage but not enough current to properly charge the battery.
I've seen alternators fail after within a year.
Perhaps a brush is sticking. Did you tap the alt. with a hammer (in a sturdy location)?
Just a few ideas.
Good luck.
carpool wrote:

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