View Full Version : battery light always on ?

04-29-2003, 01:16 PM
Battery reads 12 volts when ignition is off, 14.6 volts when running. The Battery light remains on at all times. Any suggestions?

04-29-2003, 04:12 PM
Could still be an alternator. Go down to autozone and have it tested to see if it is still making acceptable peak amps. You can have an alternator put out enough voltage but not enough amps and it will somtimes drain the battery down. Take your car down and get it tested and see where it is at from there. Once you can eliminate the battery and alternator then you can start on other things. You have to remember that a battery can read 12.6 volts just sitting there but drop to almost nothing when it has a load on it.

Test battery, test alternator. And no, pulling the cable off the battery is not an acceptable way to test the alternator.

04-29-2003, 04:34 PM
Easier yet. Start the car. Turn on all accessories including the A/C, headlights, rear window defroster, radio, wipers. Then measure the voltage. If its 14 or so, then alternator is providing enough power. If its less, then the alternator is weak. The light is turned on by the regulator circuit on the alternator itself. It is possible that it is malfunctioning. As long as the alt is making power, you can learn to live with it, disconnect the bulb or wire, or replace the alt. Of course without thtat light, if the alt should actually break, you won't have any indication other than a slow start or dim headlights, etc.

04-29-2003, 05:26 PM
well like 1badSC said, an alternator can be putting out 14 volts and still drain the battery, if it has a bad diode or something. the light should definitely not be on, and i would not simply disconnect the light!. Why they didn't put a voltmeter in the SC i'll never understand.......

04-29-2003, 08:13 PM
My SC did something like that. The alt was putting out 14 Volts when running and 12 when off. but my battery light was on. I was told that the alt for the SC is not made for charging. Like if you killed your battery and got a jump it could ruin the alt. It says that the alt is internally regulated or something like that. Take it out and take it to autozone and have it tested more than likely it is a bad diode.

Hope this helps

04-29-2003, 10:19 PM
Do as TbirdSCFan suggested this is a valid test. Turn everything that draws power. Roll the windows down as well while watching the meter. If it drops below 13V it might have a Doide or 2 out as suggested earlier.

An alternator cannot put out 14V and also discharge the battery. The problem is that at idle with everything off there is no load on the system (very little), but when you start running accessories like AC, lights, windows etc. The load is greater than what the alternator can put out so the battery has to make up the difference. That's when the discharging of the battery happens.

Or there just might be a problem with the wiring for the light. All I can remember about the batt light circuit is that in order for it to light the potential between each side of the light for it to light up. So basically if the voltage from the alt is too high or to low it will light.

There are also a few that had problems with the wiring from tha alt.


04-29-2003, 11:41 PM
Just to clear things up, there is no alternator that is made for charging a battery to full charge. When a battery is dead or drained the alternator works at 100% max trying to recharge the system, the problem is that the alt. was not meant to do this, so then it burns out from running 100% all the time trying to charge the battery. That is why it is recomended that you charge your battery all the way if it was drained. Otherwise you can kill the alt. on any car.

04-30-2003, 08:03 AM
Thanks, I'll look at the alternator more closely.

04-30-2003, 11:53 AM
an alternator is designed to MAINTAIN the battery's charge, on any vehicle, not just the SC. The 12 v you are getting with engine off is simply battery voltage, there is no alternator 'output' with engine not running. And yes, and alternator CAN put out 14 volts and still not charge the battery properly. An alternator generates "alternating current" much like in your house. your battery only accepts "direct current" or DC voltage. If the circuitry in the alternator that converts AC to DC (i think it's the diodes but i may be calling it the wrong thing..) is bad then the battery will not take a charge.