My battery light came on (while the car was running) today for the 1st time in over 5 years with my civic. Even with a dead battery, the light never came on while running. If rev the engine to 3000-3500 rpms, the light starts to fade, so I suspect that the alternator is about to go (very soon). Now, this car has about 200k miles on it, but I suspect that the alternator was changed out once around 120k miles, but it may still be the factory alternator.

Now, since it just happened today, it seems I can still start my car (suspect that its purely running off the battery)

Any other ideas for troubleshooting?

Thank you

Sean

Check the drive belt. Usually they are the serpentine belts with the spring tensioner, and stay tight until they break, but it won't hurt to look at it, unless you get your hand in it. Also check your connections, both the heavy black wire running from the alternator and both battery cables. Remove the negative cable from the battery before touching the hot ones. Otherwise, one slip of the wrench makes a big, bad short circuit.

If you have a voltmeter, check the voltage at the battery with the motor a little above idle. If you have about 14 volts, the alternator is working. Problems in the light circuit could cause over charging destroying the battery, alternator, or both.

Yea, I suspected the belt possibly... haven't changed that in the last 5 years.



Ok, I'll break out my multi meter at lunch and test my battery, both while off and while running.

Also, when you say "Also check your connections, both the heavy black wire running from the alternator and both battery cables. " Do you mean verify that they are connected and with no corrosion?

Thanks for the quick repy.

Yes, dirty or loose connections including the ground to the engine or body can cause problems.

Ok, verified that the issue is with the alternator / connection to the alternator. I used my multimeter with my car off @ the battery terminals... 12.45 Volts. Normal... Then started the car... and it DROPPED to 12.1 volts. So, from what my intuition tells me, that maybe fuseable link might be broken, or another cable.

Problem is, to be able to test those, I need to lift the front end of the car to get to the alternator. Any one have any suggestions?

A lot of guys like the Rhino Ramps. I have wooden ones I made. They are much safer than jacks, and less bother than using the jack to put jack stands under the car.

Yea, unfortunately I live in an apartment complex and won't allow me to work on my car etc etc. I could probably get away with a tune up but not lifting the car up.

A friends is giving me an alternator to try. Is there any known chains that can test (bair) alternators? I'd like to make sure it works before I attempt to have someone swapp it out for me.

If your battery tested at 12.45 volts with the motor off then dropped to 12.1 volts after turning the car on, it sounds like your alternator needs a rebuild or replacement. Try this next time, test the battery with the car off, note the voltage, then turn the car on, along with the heater on high, and your lights on, the voltage should be at least 13 volts or more. It sounds like when your battery is put under load, your alternator is unable to supply the necessary voltage.