common faults on alternator. on 2006 Jeep Commander

my alternator charge light comes on and only goes off at high revs,>3000 also makes whinning noise which continues and dies down after engine stops

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2 answers
sounds like a bad regulator in alt and poss a bering issue also
PCM regulated ,maybe have scanned to watch for proper control. Pulley poss. is 'clutched' that or bearing ,as globalhelper mentioned may also be faulty.