Funny things happen when voltages get flakey.
The electrical warning light is a charging system warning light. Although it could be just a battery with flakey internal connections, it is more likely to be an alternator problem.
Before you can get an accurate alternator test, you must qualify the battery. Get it checked out, and replace it if needed. Once you have a known good battery check for voltage up about 14.5 volts with the engine running at about 2000 RPM with no electrical accessories on.
Before replacing the alternator, check out the alternator wiring, especially the mega fuse between the battery and the alternator.
