Car Forum World

I recently just changed my battery & alternator and got my car to run doing this, but now my battery light stays on, what is the problem ?????

Check all connections at the battery,alternator,alternator belt tension,etc.,and all the ground straps at the engine and body.Check the voltage output at the battery and the alternator that should be 13.5 to 14.5v at both ends at idle. If that is all good you have some other problem.If that light is still on wiggle the wiring harness around a bit while the car is running and see iff the light goes out,if it does you may have a short in the harness someplace.

Your car may still not be charging. The light needs 12.0 volts or more on one side and battery voltage on the other, with that it monitors if the charging system works.

Get yourself a cheap volt meter or go to your local auto parts store and let them test it out for you. be sure you're to get at least 13.2 volts or more with the car running.

You also may have to tighten your alternator belt more. be sure you don't overtighten it thou..

Good Luck

Ummmm, the alternator isn't charging?

Check the voltage on the big Batt terminal of the alternator with a 'digital' volt meter, while the engine isn't running. you may want to have 12.7vdc ± .2 volts with the engine not running, which is the voltage of a completely charged battery. you may want to have the same voltage at the alternator as you have at the battery. most are around 12.7vdc

Then, check the voltage of the alternator while the engine is running at somewhat higher than an idle 1200rpm or higher . It should be about 13.8vdc, ± .2 volt.

If then check the voltage at the battery while the engine is still running. It should be the same or almost so as the voltage output of the alternator.

If it is not, you most likely have a faulty alternator or a wiring problem.

note the . before the voltage tolerance.that reads as 'plus or minus point two volts'.

is it just the battery light? If it may just be the sensor.. it can be replaced.

before you go crazy, check you fuses, start simple