Battery Idiot Light

so anyone got a guess?

Have you checked the transmission?

How old is the <...Battery Idiot...>?

Battery is about 6 months old.

We bought the car from a dealer, and on the day it was time to take it, when we went to start it, the battery was actually dead, so right in front of us they put in a new one.

So you've only had this vehicle for six months. It sounds like your alternator is failing. Now where and how it is failing could be any of the WAG provided so far. You could also have some dead diodes in the alternator.

Depending on which engine you have under the hood, you can get a new alternator for $90 to $150. You'll have to install it yourself. Better yet, take this to a shop which can properly test the alternator under load and inspect your wiring harness. This will cost you more money but having knowledgable hands and eyes on this vehicle can pay for itself in the long run.

Altenator integrated voltage regulators have some kind of overheating protection. If for some reason its temp goes too high, current capability is limited or even cut off completely untill temp comes back to normal. This of course does not exclude the possibility the overheating is because of some other alternator fault. A problem like that is not that easy to diagnose with a voltmeter only. It may for example just be the brushes, being at their end of life, make contact intermitently. S.M.

I'd start by cleaning up the posts and terminals at the battery. A lot of times you'll find corrosion in the accessory wire connection at the terminal, that you can't see while it's in place.

Remember to make a note of the security code of any in-vehicle entertainment unit before disconnecting the Battery Idiot!

toss all that data out and go right to the source, start with a fully charged battery and test the alternator AT THE alternator. bypass the lighter entirely.

the indicator light sounds defective after seeing the results of your scientific testing....I'd disconnect it, sounds annoying to me

Take your ten year old car to your neighborhood auto parts store and ask them to read your stored error codes. Most stores will do this for free. This may not tell you the root of your problem but it should eliminate a lot of speculation. I suspect that your meter is too slow to display the brief faults. I agree that the first likely bad connection point is at the battery terminals. Don't forget to check the connection points to the alternator. A mechanical cause can be a glazed or loose belt.

The automotive section is now part of Transportation (last one on the list).

I agree with #4 for your question, check the brushes first. Not a big job (once you've got the alternator off, which is a pig on some modern cars). I've known cases of warning light coming on intermittently or faintly, but with no obvious lack of charge (I didn't test it, it was 40 years ago and I didn't have a meter) but renewing the brushes cured it.

A common cause of this type of problem is often the AC compressor clutch.

As the clutch material wears over time the gap/clearance between the magnet and the "pole piece" increases/widens.

This requires higher current to engage the AC clutch and during initial AC "ON" cycle the current demand can exceed the output capacity of the alternator.

Maybe the dealer replaced the stock alternator with an old Cavalier alternator they had lying around?

Does the light come on only during city/stop and go driving? Or does it happen while cruising down the highway too?

bOTH LOW SPEED AND HIGHWAY,

They can be found on internet auction sites too.

Is your fan belt slipping? .... properly tensioned?

Is there any corrosion/grease/dirt on the mountings for the Regulator/Brush assembly?

Reg/Brush assembly mounting screws tight?

Are the brushes and slip rings clean and in good condition?

Resistance in the Reg/brush/field circuit would give good performance at light load and poor or intermittent performance as the load increases...... I have had it happen to me!

Tighten your alternator belt. Oh wait, its a serpentine belt. Well, check it anyway.

Modern voltage regulators will drag the RMS of even half wave rectification up to a good "looking" value, but you still only get half the energy out of the alternator. If I hooked up my oscilloscope to it, you could see it right away. But you probably don't have one of those just lying around like I do. And modern sound systems are so well filtered you probably would not even hear it on an AM channel. (assuming you HAVE an AM setting on your radio!) But last time I saw a snag described the way you described this one, thats what it was.

If you feel like a challenge, you can get a diode replacement kit from (insert auto parts dealer here) which comes with complete instructions for a rebuild. Or you can drop into your local wrecking yard, and ask them for a random chevy alternator which fits. Or drop a hundred and a quarter bucks on a rebuilt one. I

And if thats STILL not fixing it, then come back here, I have a lot more things to try. Fault codes should be read, and battery terminals should be cleaned as a matter of course. Bearings on your AC pump should be checked...if they are failing then you might get intermittent overloads. Come to think of it, bearings on any of the accessories or idler pulleys on that belt are suspect. But suspecting bearings is a bit of a reach...I tend to suspect them because they are moving parts. And they have the potential to do intermittent things that solid state components just don't do.

Sounds like fun. Hope you don't need the car to get to work! I "like" snags like this.

I may be the only one in the world who does!

A six month old battery should still be good, but in the rush to put the new battery into service did they overcharge or put dirty water in the battery? Was it a new battery or one that was just lying in the back of the shop, steam cleaned and put into YOUR car. Sometimes this happens when the customer is standing there waiting with "that look" on his face and the salesman's face is going increasingly red.

At least your idiot light comes on.

I had two GM vehicles in the '90's, both of which suddenly died on a hot summer day because the alternator failed and the first indication I got was when the engine stuttered and then died. No warning whatsoever. I was stunned, I couldn't imagine the GM cost cutters had eliminated the battery idiot light.

I figured the 1st incident was a fluke, but after the 2nd incident, I bought a cheap voltmeter and wired it to a cigarette lighter plug and kept it plugged in as a permanent meter.

My next car was a Toyota.

Battery Idiot Light...hmmm. Follow the other posters hints about terminal cleaning, if the posts are corroded, or lugs are loose, then yeah, you could have a transient.

If you had been driving a Cavalier, I would say maybe that was an idiot detector, but sorry I just could not resist.

My wife did have a cavalier,

It was a great car while we had it. Till intermittantly it would run really rough. I mean really bad, couldn't figure it out at all because it was soo intermittant. love those things that do things and then stop. She got her miles out of it, she bought it for like 3 grand with about 80K on it, and when she sold it to a teen ager for 1 grand she had like 280K on it, he said he wanted it even with the "Problem" about a year later he stopped by with the car and said it too 6 monthe to figure it out, but it was one of the ignition coils would die, Just one, so it would turn into a 2 banger intermittantly UG!

Cavalier used 2 coils to fire 4 cylinders.It fired 2 plugs at the same time,but only one would be at the top of the compression stage so it worked--sometimes.What a cheap arse way to build a car.

The back windshield blew out at 60 mph when I had the windows down on a hot day.

Fortunately, no one was behind me on the rural road.I went back and got the windshield,it was not broken, and looked for what held it in.Nothing but some type of glue,and it had failed.No clips,molding or anything.I reinstalled it myself with a poly adhesive and it stayed till I finally got rid of it.The outside mirrors fell out of their mounts, and the same thing:Hot glue failure.I reinstalled new ones with silicone, and they stayed put. And people wonder why GM started going Belly Up.They should have been allowed to die an ignominious death.I would not have attended the funeral,but I would have sent them a card saying that I approved of it.

Now we,the public are the proud owners of this lodestone.Do not believe the company when they say they have repaid the loan.They simply moved funds from one book to another to try to fool the gullible.

When a company stoops as low as GM did, it will take at least a generation to recover.I will NEVER buy another GM vehicle of any kind.Once burned, twice shy as they say.

GM discovered that they could make more money by financing the vehicles than they could by making them(GMAC),so they quit giving a sh--t about quality.

I hope to see the demise of GM in my lifetime but they are "TOO BIG TO FAIL"(Translation for the gullible:They contribute too much to the politicians).

Cynical?Sure,but GM made me that way.

I now drive Ford Trucks, Harley Motorcycles, and Honda cars.

As I said before, my sympathies on your purchase.