Start by measuring the battery voltage with the engine off and again with it running. A fully charged, good battery will read 12.6 volts. If you find 12.0 volts, it's good but discharged. Closer to 11 volts means the battery has a shorted cell and must be replaced.
With the engine running, the voltage must be between 13.75 and 14.75 volts. If it is low, and the battery is not shorted, suspect the generator.
Tuesday, January 10th, 2012 AT 4:04 AM