12.7 or 12.7 volts is insufficient charging. You need the alternator to be charging at 13.5 to 14.5 volts.
With engine running, turn on all electrical equipment and test the charging voltage. Run the engine for a longer period and check again. If it is not as specified, the alternator is bad.
Btw, test the charging voltage at the alternator main wire. If it is alsmot similar to the voltage between battery terminals, the wiring should be good.
Monday, June 3rd, 2013 AT 2:23 PM