Hey everyone,
On my way to work this morning I experienced a surprise to find my battery warning light on as I was driving down the freeway. The battery warning light would then turn off when I approached a stop. Once I accelerated again the light came back on. This happened repeatedly until I arrived at work. The terminals are snug and look fine, and the battery is fairly new. Any ideas??? Could it be the alternator? How much will that cost??? Thanks for the help.


Ryan

 

It's interesting that it turns back off at low speeds. Have you tried slowly revving the car while you're stopped to see if that gets the light to come back on? Or shifting into neutral while you're at highway speeds and seeing if the light goes off?

I don't know if the battery warning light warns of too-high voltage in addition to too-low voltage, but if it does, it might be that your voltage regulator is failing and allowing your alternator voltage to get too high when your engine is turning at higher RPM.

I'd get a voltmeter and a friend, and have them check the voltage coming out of the cigar lighter while you're driving around. I don't remember the exact voltage limits offhand, but if it goes below 13V or above 15V or so while the engine's running, you probably have a regulator problem.

 

Go to Pepboys or one of the other auto parts places and have them do a check of your charging system. The red light means a discharge condition.

If the battery is good and the alternator (or belt is bad), then the light will go on when the engine revs speed up. If the light is on at idle and then goes off when the engine revs, then the alternator is OK but the battery is putting out insufficient power when the alternator is not charging it (although eventually the battery will get discharged to the extent that the car will not run).

Remember that the condition of the belt will have a direct effect on whether the alternator charges and just because the wires look tight, that does not mean that the contacts are good, particularly the ground.

BTW, in the meantime, don't run accessories like the lights, radio, etc more than you have to before getting it checked.

I agree with Scott that there are other aspects of the system like the voltage regulator or even an intermittent short in the system that may be the cause. Get the charging system checked.

 

I'm going to try and take it over to autozone or pepboys today. I appreciate the useful advice.