QuestionI have a 2005 Hyundai Elantra (2.2L engine). Last night my dash lights and head lights began dimming, and engine would rev whenever started. Then the battery indicator light came on and stayed on all night. While checking to see if I could disconnect the alternator to have it checked, the battery indicator light went off. What could cause this? If light went off, do I still need to worry?
AnswerThe battery lamp indicates that the alternator is plugged in and not charging.
Check the alternator belt to be sure it is tight. If loose, the alternator pulley may not turn under certain conditions, preventing charging. This is most likely not your issue, as a loose belt tends to manifest itself more when the engine is cold rather than at operating temperature.
If the battery lamp again illuminates, turn the engine off, unplug the alternator electrical connector-- do not touch or remove the bolt-on terminal-- and turn the ignition key to the on position. If the battery lamp is not on with the connector unplugged, you've just verified that you do not have a short in the wire that triggers the lamp.
Once you've verified that the belt is tight and there is not a short in the wiring, it's safe to assume that the problem is within the alternator itself. This is in fact the most likely scenario considering your symptoms. Often alternators will stop working as they get hot and then start working again as they cool off.
And, as implied, you should be concerned even though the lamp is off now. The fact that it came on in the first place indicates you had a problem with your charging system. It's not very likely this was a one-time incident.
