The best way to see if there is a fluctuation in the charging system is to test the actual battery voltage at the posts with a multi-meter. Setting the multi-meter to DC voltage touch the leads to the battery, with the engine running. If the voltage in the battery fluctuates, normal voltage is 12-14.4 while running but at a steady state, like the volt meter, then there is a charging problem or the battery could have a dead cell.
To test the battery, perform a the same test with the engine off and see if the voltage is stable. It will be 12 volts unless just driven and then it will be between 12-14 volts.
If there is a charging problem then the alternator needs to be tested and the most common problem is the voltage regulator.
Tuesday, December 6th, 2011 AT 10:46 PM