AO Silver Member
Join Date: Mar 2003
The warning light is measuring an imbalance somewhere. So, as the previous poster said, a poor earth would cause this. Also a failing alternator would show up on this light. You can run some voltage checks.
A fully charged battery should read about 12.6 volts. If the battery reads 12.4 volts or less, it is low (discharged) and needs to be recharged.
After charging the battery or jump starting the car, connect the voltmeter to the battery. A charging system that is operating normally should produce about 13.5 to 14.5 or more volts at idle. If the charging voltage is less than 13.5 volts, the alternator is not putting out enough current to keep the battery charged.