battery light [Archive] - Forum


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05-12-2008, 10:14 AM
hey guys question .my wife car the battery light was coming on.she went to work and it just died as she was driving.i changed the alternator .everything fine pushing out the right amps or volts but the battery light is still coming on...and kind of feels like its going to stale when its idling ....any ideas what the problem could be?

05-12-2008, 10:22 AM
A Battery Light is an indication that either the charging system is not functioning at all or at least not properly.

You say you changed the Alt.

First thing would be to check the Voltage at the Battery while the car is running. Verify the Voltage at the Battery is correct (It should be above 13.5). If that is fine then you should be somewhat ok.

The reason I say that is because the Battery could be a low voltage which could also trigger the light. So check the Voltage at the Battery with the car off as well and verify 12 volts.

It should be either you have a Bad Battery or Bad Alternator.

05-12-2008, 10:27 AM
battery fine its reading like 12.7 volts and when on its like 13 something so battery was tested its fine and there is a new alternator so everything reading fine but the lights still on and again kind of feels like its going to stale when its idling

05-12-2008, 10:38 AM
If the Battery is Good and the Alternator is Good then Light should be OFF.

This warning system is very simple, unlike a SVS or SES light which could be multiple things.

I would have a Shop look at it and see if something has good horribly wrong electrically. I doubt it but I would not suggest driving with a Battery Light on unless you know what the problem is.

05-12-2008, 10:43 AM
thanks and ya i am not driving it and i was thinking of bring it to a shop to check it out..thanks again

Lab Rat
05-12-2008, 11:20 AM
I would clean the cable ends and terminals. Sounds like your "new" alternater is not charging your "new" battery. Otherwise something is definately FUBAR.

05-12-2008, 12:36 PM
lol thats what i think i a fubar big time

05-12-2008, 06:59 PM
What about the volage regulator?

The voltage regulator controls the rotor field current in order to limit the system voltage. When the field current is on, the regulator switches the current on and off at a rate of 400 cycles per second in order to perform the following functions:
Radio noise control.
Obtain the correct average current needed for proper system voltage control.
At high speeds, the on-time may be 10 percent with the off-time at 90 percent.
At low speeds, the on-time may be 90 percent and the off-time 10 percent.

Since you changed it, did you verify that the alternator is the correct one for your vehicle?

Here is a schematic diagram of the charging system.
Hope it helps.