have it bench tested, may be some other issue. Check battery terminals for corrosion. Look on internet and can find new ones for reasonable price. The aftermarket remans are generally fair, and have a good warranty.
Don't know how many miles you have on it,I've fixed both my alternators with a new set of contacts like $12
One had 325k on it when the engine it was on went TU.
The one in the truck now has nearly that many miles too.
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