ok, so I started my car yesterday and the battery light flickered a bit then stayed on. i turned the car off immediately and checked over things. Started it again and no battery light until I pulled out and hit the end of my street, after I started going again the light went out and has not come back on. The other symptom that has cropped up at the same time I noticed driving home from work last night, my interior lights dimmed briefly while I was driving a couple of times, but still no battery light.

I have just checked my cable connections, they are secure and clean, the alternator belt is only 4 months old and still tight, alternator connections look sound. Basically I'm just looking for confirmation that my alternator is indeed going out before I go out and plunk down $100+ on a new one.

 

also, started the car and put a multimeter to the battery terminals and it was reading a steady 12.32 DCV

 

Turn on the headlights & measure again. 12.3 volts sounds like the alternator isn't charging. The reason for turning on the headlights is to FORCE the alternator to try and charge.

 

tried that, and with the headlights on, the multimeter dropped to 11.98 DCV. safe to say the alternator is gone

 

the wierd thing is, the battery light is not coming back on still, which is throwing me, i do however have some funny engine rev hiccups, and the light dimming issue.

 

Yeah, when the alternator is charging, it should be putting out 14-ish volts.

Is the battery light working? It should light up when you turn the key ON before you actually start the engine. Even so, it's that alternator (or voltage regulator) that switches the light on, so maybe that's part of what's gone bad on the alternator??

 

the battery light does work to my knowledge. I hit some debris on the interstate a few months back that shredded my alternator belt and the battery light immediately came on. I haven't driven the car today, only started it checking charging, i checked it again about an hour ago and the multimeter still reads 12.3 DCV. it seems more and more likely that the alternator is the issue.

 

Funny you mention hitting something. Here's something for you to check out. Inspect the wiring harness at the alternator; follow it back as far as possible and look for insulation rubbed off a wire, or any wires pinched & shorting to ground.

There's one of the wires in the alternator harness that can control the alternator. Not sure which one, you'll want a wiring diagram for your year car. (the "C" wire??)

When the ECU decides that the voltage is OK and the electrical loads are low, the ECU can command the alternator to shut down. It does that by connecting that "C" wire to ground. Well, if that "C" wire is shorted to ground by being pinched or otherwise allowed to short, THAT will shut down a good alternator even though it's not commanded by the ECU.

 

aah hah. I shall do that then.

 

It still could be worn out brushes in the alternator. Or a bad voltage regulator. So that "C" wire is just one more thing for you to check out.

Many parts stores will test your alternator. But if they simply have you run your engine and they clamp a big load resistor onto your battery, that won't identify the shorted wire as the real problem.

OTOH, if you remove the alternator & have them test it on the bench, and it tests GOOD, then you can really suspect that control wire.