Common mistake. I need to know the exact diagnostic fault code number, then when the description is looked up, you will see it did not say to replace the alternator. Fault codes never say to replace parts or that they're defective. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. When a part, typically a sensor, is referenced in a fault code, that part is actually the cause of the code about half of the time. First the mechanic has to rule out wiring and connector problems, and mechanical problems that could affect that circuit.
My 'puter's battery is dying. I'll be back in a little while to see if you replied back with that code number. Then we'll figure out how to start the diagnosis. At a minimum you'll need an inexpensive digital voltmeter.
SPONSORED LINKS
Saturday, June 6th, 2015 AT 6:52 PM