Had a problem a little while ago, where the battery light would come on occasionally. Fitted a second hand alternator I had spare here and it went away...for a while. Pulled into a servo to buy fuel and car wouldnt start. No charge from alternator = drained and dead battery.

Bought another alternator from the wreckers that was supposed to be still working. Fitted it and all fine....until now a month later.

Battery light is still coming on, this being its 3rd alternator.

Did I buy another dud alternator, or would something be killing my alternators? (is that even possible? lol)

I dont fancy spending $300 on a new alternator, nor to continue buying second hand ones that will die....:tired:

have check the brushes,s in your alternator little box where the wire,s plug in

What would I be looking for, and why would they be affected on 3 different alternators?

What would I be looking for, and why would they be affected on 3 different alternators?

Agree with magnaman89, probably the brushes in voltage regulator on the alternator or it could be your battery.

As to why it would be occur on all 3 alternators... probably because they are all old second hand non-reconditioned alternators, or your battery is stuffed or you have resistive wiring between alternator and battery.

battery is just over a year old, so no problem with that.

There is a problem with voltage drop from the battery to the ignition sometimes (have to use a wire to feed the starter 12v direct), but its not a related problem.

Cant see why all 3 alternators would die so close to each other, even when they are 2nd hand. The second one I put on the mechanic mentioned that you could hear the alternator working on and off with the motor running...ie it would drop the revs a tiny bit, then kick back up when not working.

If the brushes were the culprit, then wouldnt the issue be more consistent? The light comes on for a either a few seconds, or a short time, then disappears for a week or two.....last time when the battery was drained, the battery light never came on at all before we stopped.

Age of battery doesn't necessarily mean it's not a problem (I've had dud newish batteries before).

I wasn't suggesting that the alternators are necessarily faulty, just the voltage regulator(s) which is mounted on the alternator.


The light comes on for a either a few seconds, or a short time, then disappears for a week or two.

For what it's worth, that is exactly what my TS was doing. The voltage regulator was at fault.

I wasn't suggesting that the alternators are necessarily faulty, just the voltage regulator(s) which is mounted on the alternator.
For what it's worth, that is exactly what my TS was doing. The voltage regulator was at fault.

So just replace that and see how it goes?

If i find one like Like this, (http://www.ebay.com.au/itm/MAGNA-TN-TS-ALL-VOLTAGE-REGULATOR-BOSCH-ALTERNATOR-/200641715053?pt=AU_Car_Parts_Accessories&hash=item2eb72d9b6d) is that about the right price?

Will have to find the right one, and somewhere that sells it...

wiggle the plug on the alternator so as to slightly flex the regulator, if you can hear the alternator coming and going then you can almost 100% bank on it either being brushes or internal to the reg. in either case the best plan of attack is to replace the regulator.
do yourself a favour only get a genuine bosch regulator commonly known as an RE60.
remember to clean and tension the two contacts inside the alternator before fitting the new one. also to disconnect the battery lol.
also check the plug for corrosion, this accounts for about 10% of failures. if it is corroded then it is best to replace it and the regulator.
other things to check before replacing any parts is the connection of the battery terminals (are they clean, sulphate free, on as far down as they can go, tight), the main connection in the distribution box, the connections on the fusible links, and the B+ terminal on the alternator.
A voltmeter is your friend.
this family of bosch alternators is notorious for loose internal bolts, and breaks on the spot welds inside the rectifier, so i wouldnt rule that out either.

If you're handy with a soldering iron it takes 10 minutes to de-solder the worn brushes and solder in new ones - only $5 on ebay (http://www.ebay.com.au/itm/ALTERNATOR-BRUSHES-suit-HITACHI-MITSUBISHI-5x8x18-hole-09-029-/400297303264?pt=AU_Car_Parts_Accessories&hash=item5d33941ce0). I had the same issue with the batt light and replaced mine a couple of weeks ago, perfect since!

If you're handy with a soldering iron it takes 10 minutes to de-solder the worn brushes and solder in new ones - only $5 on ebay (http://www.ebay.com.au/itm/ALTERNATOR-BRUSHES-suit-HITACHI-MITSUBISHI-5x8x18-hole-09-029-/400297303264?pt=AU_Car_Parts_Accessories&hash=item5d33941ce0). I had the same issue with the batt light and replaced mine a couple of weeks ago, perfect since!

on (almost) any other regulator out there i'd agree with you, but the RE60 is a sensitive animal, you may replace the brushes and still have an issue due to internal damage caused by spiking when the brushes make and break contact... thats why bosch developed the RE72 so much more robust

I'm having this battery light issue as well. Started out as 1 - 2 weeks between light coming on. Goes off after about 10 minutes. Then it became a couple of morning starts in a row. Brand new battery, maybe 6 weeks old after previous one was just plain dead one morning. No warning.

I have a few after market devices wired to battery. These are now disconnected and I have been tracking voltage drop which is still occuring.

I have TJ Exec. The light will come on if voltage drop gets to 12.5v. I check pre journey voltage and then end of journey voltage. I am getting down to 12.6v after 8 - 10 hours standing. After 30 minutes drive we have about 13.25v. If I drive for longer than 1 hour per day there is enough charge the next day to crank the motor and no light otherwise the normal commute is not enough.

so voltage drop is about 0.6v overnight. I have sometimes noticed the voltage drop second by second when getting a reading. Take a reading and it's Xv. Clear that and then take another and it will be -0.1v than before. Obviously if the radio is on, the voltage drops and it does it quickly at about 0.1v per couple seconds.

So I was unsure where to start looking. I intially thought Alt or Reg but with the level of voltage drop I became unsure. Does my problem sound like it fits with the OT?
I have a couple of other questions and would really appreciate you guys advice.

How hard is it to replace the Reg?
How hard is it to do the brushes? I assume thats pull the thing out and solder in the new brushes. Do you need to deal with belt tension if these things need to come out for this and does that require any thing special tool wise.

Thanks

Just want to say that if you have had to remove the battery terminals at all, or jump start the car, its possible you hooked up the battery the wrong way around. If the alternator has seen reverse polarity, the diodes will be blown. Thats something not worth fixing, as there are at least 6 internal diodes.