Hi all. I hope someone is able to guide me in the right direction. My wife's TE has an battery warning light that's staying on and I have no clue why. Basically, the car was being driven one day, then all of a sudden the tacho, speedo switched off (like if you turned the ignition off) and the car kept running. Once the car got to the traffic lights and stopped (it's automatic) the car died and didn't start again. Once towed home, it started after a few hours and the battery warning light stays on. I replaced the battery with a brand new one as the battery was a few years old, but didn't fix the problem.

I stuck a voltmeter on, batter is 12.?? volts with the engine off, and with it running it's 12 or 11 volts. I checked the alternator relay and they is working fine. I looked at the fuses with appear ok. I brought a 2nd hand altnernator from the wreckers and swapped in it, and the battery warning light is still staying on and the with the engine running I'm still only getting 11 or 12 volts at the battery. Did the same test on my 380 and my fathers TE and with the engine running I got 14.?? volts.

I checked cables connecting to the alternator and found one where the insulation was cracked and a bit was broken away. I rapped that in electrical tape a few times just in case it was shorting on something, but it hasn't fixed the problem.

Any idea's what else I can do to fix the battery charging warning light that's staying on and to get that charge to 14 volts?

I brought a 2nd hand altnernator from the wreckers and swapped in it, and the battery warning light is still staying on and the with the engine running I'm still only getting 11 or 12 volts at the battery. Did the same test on my 380 and my fathers TE and with the engine running I got 14.?? volts.


Your original alternator is worn out.
So is the one from the wreckers. (Been there, done that - took it back, got another non-functional one)

Take either alternator to a car parts shop, they will swap it for a working one with warranty. If not in stock, they will organise one.
In the meantime, put the battery on a charger overnight. The car will be ok to use with a stuffed alternator in the next day, just keep your km down, and use the charger whenever the car is at home.


PS:
14.7 volts at cold startup, fades slowly to 14.2 volts as the battery comes up to full charge. That's what you are looking for if everything is healthy.

Disconnect one of the main battery leads when charging.

Feel the alternator when the engine is cold, and the charged battery is connected. If it feels warm, one of the diodes is kaput and the battery will discharge all by itself. Disconnect battery and don't use the car until you can get a working alternator.

Sounds like the voltage regulator has given up, mine did stuff similar to that except the battery light didn't work at all due to a bad connection. All fixed when I replaced the voltage regulator.

Sounds like the voltage regulator has given up, mine did stuff similar to that except the battery light didn't work at all due to a bad connection. All fixed when I replaced the voltage regulator.

Isn't the voltage regulator part of the alternator and if not where do I find it. Stupid question but never needed to check one before.

Yes it is, at rear of it. It can be replaced on its own. Best to take it to an auto electrician and get them to recondition the whole unit. It can be a worn brush or faulty regulator.

Have you checked the wiring, in particular the sensing line. Looking at the manual there is a fuse for it (No.16). There is also a few other fuses for the light side of things. Best to check all the fuses and the fuseable link for the alternator connection. The odds of having 2 dud alternators is slim.

The odds of having 2 dud alternators is slim.

Not in my experience.
Mine went, got one from a wreckers, it was stuffed too. Went back and swapped it - that was stuffed as well.
Finally went back and swapped it for a starter motor, and took my alternator in to get reconditioned. That didn't last long, took it back under the 3 month warranty. Finally ended up with a working one. Something about Bosch used alternators . . . lol

Have you checked the wiring, in particular the sensing line. Looking at the manual there is a fuse for it (No.16). There is also a few other fuses for the light side of things. Best to check all the fuses and the fuseable link for the alternator connection. The odds of having 2 dud alternators is slim.

I have checked some of the wiring. Found one of the wires coming from the plug on the alternator, the insulation was hard and brittle. I taped up with electrical tape the section where bare wire was showing. Didn't make any difference though. What is the sensing line? As far as the alternator goes, I understand that age, etc alternator from a wreckers one won't be crash hot BUT logically I'm unsure that the original alternator and the wreckers one will have the exact same problem with the exact same symptoms. Having read MadMax's post I don't disbelieve it, but I'm struggling to see it being the exact same cause.

There is only one symptom really: IT DOESN'T WORK!

I think a reconditioned one will have new bearings, turned commutator, new brushes and (possibly) new regulator and diode packs.
Often the aging Bosch will wear out the brushes, and the regulator or diodes go out in sympathy. Electrical spikes from the on/off charging the alternator is doing with worn brushes, possibly. That's the story I got from the guy who reconditioned mine, anyway.

A recon + warranty = all problems solved.

Costs: (roughly, some may be out of date)
$5 for a pair of brushes.
$60 for a regulator.
Wreckers $60 (?)
$160 for a recon.
$350 for a brand new one.

Feel free to try all possibilities. lol

I suspect that you now have 2 dud alternators. Try to get your money back from the wrecker. It is possible that you have a short circuit somewhere in your system, which is dragging the voltage down to the point where the idiot light comes on on the dashboard, but I suspect that it is the alternator itself.

For what it is worth, I suspected I had a faulty regulator in my wife's TF Magna. Whenever the aircon came on at night, the headlight intensity would drop noticeably for maybe half a second, and then it would catch up again. I decided that I would replace it when it failed totally, but over 14 years and 200000 km later it still had not failed when I traded it on a new car.

No short. Any short in the wiring would blow a fuse, and if it is inside the alternator, it would get warm to the touch.

The "idiot light" is not just a warning light, it is a light in the 12V supply to the alternator's regulator to excite the stator coils when the ignition is turned on. Once the alternator produces voltage, it raises the idiot light circuit to 12 volts, effectively giving no voltage at the light and putting it out. If the alternator puts out 0 V, the light stays on.

"The "idiot light" is not just a warning light, it is a light in the 12V supply to the alternator's regulator to excite the stator coils when the ignition is turned on. Once the alternator produces voltage, it raises the idiot light circuit to 12 volts, effectively giving no voltage at the light and putting it out. If the alternator puts out 0 V, the light stays on. "

If the poor guy is getting no voltage, maybe there is a fault in the exciter circuit and the alternator is not getting the signal to fire up the alternator?

Sure. The brushes are worn out and the stator isn't getting the message.
In short, he needs a new alternator.

Hey all. Just wanted to say a big thanks to everyone for your help and advice.:bowrofl: But the prize goes to MadMax. Work has been flat out so I couldn't do much during the week but yesterday afternoon after work I got the alternator swapped at the wreckers. Got back home and bolted it all in. Started the car up and (expecting no change and for me to spend the entire weekend trying to find what's wrong) the charging light on the dash went out immediately. So I attached the volt meter and with the motor running I'm getting the 14.2 volts I'm meant to get. So believe it or not, I managed to get another alternator that had the same problem as the original one. Think I'll go buy a lotto ticket! Again cheers everyone. :)

Perseverance pays off! lol

Apologies for hijacking, but my battery light currently flickers on/off while the car is still with brake light on. I tested the voltage and the battery is 14.2 with everything on and around 12.7 off. Is this a sign my alternator is on the way out and should I replace?

Apologies for hijacking, but my battery light currently flickers on/off while the car is still with brake light on. I tested the voltage and the battery is 14.2 with everything on and around 12.7 off. Is this a sign my alternator is on the way out and should I replace?

Is it worse with lights and ac on? What is your idle speed at and does the charge light flicker in N with brakes on?

Vlad, i tried with AC and lights on and in Neutral, but could not replicate the problem. Doesn't seem to happen consistently, idle is fine...

It could be the beginning of the end of the alternator/regulator or lose cabling.