CHEVROLET SILVERADO ALTERNATOR

My Truck Seems To Have An Alternator Problem. When Hot, The Voltage Will Drop To 12.5 Sometimes And Stay There, Then For No Reason, Jump...

I Need To Replace The Alternator

When Cold, My Alternator Charges Around 14.5 To 14.9 Volts. When Everything Warms Up, It Drops To About 13 Volts. Is This Normal...