The "Battery" warning light means it is not being recharged by the alternator. To prove that, measure the battery voltage with the engine off, then with it running. With it off, 12.2 volts means it is okay but discharged. Charge it at a slow rate for an hour, then remeasure it. A good, fully-charged battery will measure 12.6 volts.
With the engine running, the battery voltage must be between 13.75 and 14.75 volts. If the alternator isn't working, you'll find the same as in the last step. There are a couple more voltage measurements to take before condemning the alternator.
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Thursday, February 19th, 2015 AT 10:49 AM