02 330CI Battery Light stuck on.

[Bandit959]

Hey Folks....
I was hoping that someone could answer this.. Here's what's going on...
- 02 330Ci with 113K miles. Original alternator
- Battery light came on the other day. Just when my recommended "service in" mileage clicked to -1025 miles. It's off.. I'm due to for service in about 500 miles.
- Check the battery voltage using the in-dash diagnostics. Battery has 12.5v when idle.
- Started the car and check the alternator output: 14.0-14.2v unloaded
- Turn on the blower, radio, headlights, foglights and cabin lights and the voltage bounces between 13.7-13.8v
- Turning everything off and the output goes back to 14.0-14.2v
- Shutdown the car and the battery voltage is 13.0v
- Visually inspect the battery, the eye is green (I know just 1 cell) but more to check the connections. No corrosion, both leads are secure.
- Attach a voltmeter to the battery and see the same behavior as above.
- Behavior is constant. For the past 3 days there have been no changes.
- I'm planning on bringing it to an independent shop next week. Soonest I could get in.
- I'm going to swing by Autozone and have them test it as well.

But I'm looking for your thoughts. This doesn't sound like a failed alternator to me. Given the miles, maybe it's failing? Would resetting the service mileage clear this?

Any thoughts would be appreciated!

[Jack Dabsy]

Sounds like the alternator is fine...
A reset may not clear the charge light, but still worth a try!
It could be a fault in the dash itself, or a poor connection "After" the alternator to the dash or fuse box... Best I can do without being there... Good luck!

[Bandit959]

Hi Dabsy....
That's kind of what I felt. I'll see if I can get to it this weekend and check teh alternator for loose connections.

[brettski]

It might be worth disconnecting the battery for 20 minutes or so and see if anything is different after you reconnect the battery.

[Bandit959]

Hi Brettski...
I had the battery disconnected when I did a visual inspection of the posts. But it was disconnected for maybe 5 minutes max.

I think I'll try your suggestion later on tonight and disconnect the battery for longer and see if that clear it. Thanks!

For completeness, I took a look at the fuze box diagram to see if there was one specific for the alternator/battery but didn't see one.

As Dabsy suspected, the reset didn't work clear the light. It was worth a shot!

[Jack Dabsy]

Here's a little info on the charging system...
As your alternater "seems" fine, they have either an inbuilt system, or Wiring Loom intervention where the battery cannot send power back to the alternator... It's usually as simple as a "Diode" in many cases...
I know this doesn't help at the moment but sometimes an alternator can appear to work perfectly but still have a fault !!
Just a thought, buddy...

[Bandit959]

Originally Posted by Dabsy

Here's a little info on the charging system...
As your alternater "seems" fine, they have either an inbuilt system, or Wiring Loom intervention where the battery cannot send power back to the alternator... It's usually as simple as a "Diode" in many cases...
I know this doesn't help at the moment but sometimes an alternator can appear to work perfectly but still have a fault !!
Just a thought, buddy...

I tried disconnecting the battery for an hour per Brettski's suggestion. Didn't work but again worth a shot.

I suspect that you're right Dabsy. It does *help*. I'm going to let an independent shop take a look at it just in case it is the dash, some wiring connection that I can't see or whatever. SO that extra bit of info will be useful when I talk with them.

If I knew it was the alternator for sure, I'd pull and replace it. I don't want to waste a bunch of time getting parts and replacing something to find out that I was wrong.

I'll know for sure Wednesday and let everyone here know. Maybe I can add a bit to the knowledge base here. ;-)

[Bandit959]

Just a follow-up for everyone...
- Yesterday, the alternator light began flashing intermittently kind of like a loose connection and finally went out after a few minutes.
- The alternator light did NOT illuminate when starting the car, like there is no connection to it.
- The alternator light DOES illuminate when an instrumentation test is done.
- Checking the voltage, I got 12.3-12.4v. Started the car and checked the output of the alternator. It appeared that there was no output from the alternator because all I’m reading is the battery. (12.3-12.4v).

So I brought it into the shop. They informed me that Voltage regulator had failed. They could replace the part in the original alternator but for about the same cost, put a rebuilt Bosch alternator in. Since it was the original alternator, I went that way.

The tech explained that the light does go on when the voltage regulator is failing. It noticed fluctuations in the voltage. I personally didn't see that in my testing but since it wasn't working at all, that makes sense.

So you CAN have the alternator light on and have everything appear to be normal. You're just on borrowed time.

If I had known that before, I would have opted to replace it myself. Live and learn I suppose.

[witeshark]

Glad it seems sorted.