Car alternator failure -- twice!

[Sparky]

Last year the alternator on my Toyota cooked the stator windings. I didnšt
look any further and replaced it with a rebuilt alternator & regulator from
the local parts supplier.

Now (7 or 8 months later) the replacement has failed in the same mode. Išm
suspicious. Also confused:

If a diode opens there wouldnšt be an increased load on the stator windings.
If a diode shorts, there also wouldnšt be any increase, just a decrease in DC
output voltage.

If the alternator output is shorted, since itšs connected directly to the
battery (+) terminal, this would result in smoke and fire, at least a burnt
fusible link. None of this has occurred. (Well, the windings are discolored
and the smell is what clued me in to these problems.) When I put in a
replacement alternator Išm quite confident everything will look just fine.
Until next time.  

What could cause these symptoms? Twice?

Thanks!

 

[Rich.]

"Sparky" <see@thesig.net> wrote in message
news:0001HW.D1073825006CBD3AB01029BF@news.eternal-september.org...

Last year the alternator on my Toyota cooked the stator windings. I didnšt
look any further and replaced it with a rebuilt alternator & regulator
from
the local parts supplier.

Now (7 or 8 months later) the replacement has failed in the same mode. Išm
suspicious. Also confused:

If a diode opens there wouldnšt be an increased load on the stator
windings.
If a diode shorts, there also wouldnšt be any increase, just a decrease in
DC
output voltage.

If the alternator output is shorted, since itšs connected directly to the
battery (+) terminal, this would result in smoke and fire, at least a
burnt
fusible link. None of this has occurred. (Well, the windings are
discolored
and the smell is what clued me in to these problems.) When I put in a
replacement alternator Išm quite confident everything will look just fine.
Until next time.

What could cause these symptoms? Twice?

Thanks!

Did you change the battery any time after the alternator was changed or is
it the same one still?

 

[Tauno Voipio]

On 16.2.15 16:01, Sparky wrote:

Last year the alternator on my Toyota cooked the stator windings. I didnšt
look any further and replaced it with a rebuilt alternator & regulator from
the local parts supplier.

Now (7 or 8 months later) the replacement has failed in the same mode. Išm
suspicious. Also confused:

If a diode opens there wouldnšt be an increased load on the stator windings.
If a diode shorts, there also wouldnšt be any increase, just a decrease in DC
output voltage.

If the alternator output is shorted, since itšs connected directly to the
battery (+) terminal, this would result in smoke and fire, at least a burnt
fusible link. None of this has occurred. (Well, the windings are discolored
and the smell is what clued me in to these problems.) When I put in a
replacement alternator Išm quite confident everything will look just fine.
Until next time.

What could cause these symptoms? Twice?

Thanks!

Bad battery which does not let the voltage to rise, or too much load,
but not enough to blow the fuse. A winding can be fried with a slight
overload and limited cooling.

Do you happen to have quadruple 300 W audio channels on board?

--

-TV

 

Alternators are shit today. In the old days you could replace one, take the cablesoff a good but completely dead battery and start it with a another and then connect the battery to charge. Sometimes it would slow down the engine because of the load. A dead but good battery is almost a short circuit. Those old alternators could handle it but not the new ones. It even should says in the instructions to make sure the battery is charged before starting that car after replacing the (shit) alternator. (let's not even go into a few Chevy engines where you have to damnear remove the engine to change it, and they are a high failure part)

You would not get the same thing likely with two alternators in a row unless it is a common failure. The problem MIGHT be an overload but it would be one that is only there when it is running, otherwise any short that heavy would kill the battery and it would not start the next morning.

Problem is they don't put a proper ammeter in cars anymore. I don't even want to go into telling you how to hook one up. The starter motor has to be isolated and on some cars this is damnear impossible. You don't want to read the starter amps on the ammeter, it is too high and you would need a proper scale and that would be too high to see if this is the problem.

The only real way to do it these days is at the alternator itself, that will not indicate discharge like in the old days but it can tell you how much current is being pulled. The fattest red wire on it, take it off and put the ammeter there. The alternator has a rating, if the constant drain without the headlights and AC on is near that rating there is an overload. Not a dea short so an ohmmmeter will not tell you where it is. It could be almost anywhere, one of the coils or cokl drivers, fuel pump, or some modification like those road lights or blue diamond headlights with the ballasts or who knows.

It could also be that the engine is running too hot, concievably. That is not the most likely though. It is also possible that the alternator is simply underbuilt for the car. that is actually pretty likely, it would not be the first time I saw it happen.

 

[Jon Elson]

Sparky wrote:

If a diode shorts, there also wouldnšt be any increase, just a
decrease in DC output voltage.

No, ONE a shorted diode would cause huge currents in the winding
connected to that phase. Two shorted diodes on the same
phase would cause huge DC currents and blow the fusible link.

Jon

 

[Martin Riddle]

On Mon, 16 Feb 2015 06:01:09 -0800, Sparky <see@thesig.net> wrote:

Last year the alternator on my Toyota cooked the stator windings. I didnšt
look any further and replaced it with a rebuilt alternator & regulator from
the local parts supplier.

Now (7 or 8 months later) the replacement has failed in the same mode. Išm
suspicious. Also confused:

If a diode opens there wouldnšt be an increased load on the stator windings.
If a diode shorts, there also wouldnšt be any increase, just a decrease in DC
output voltage.

If the alternator output is shorted, since itšs connected directly to the
battery (+) terminal, this would result in smoke and fire, at least a burnt
fusible link. None of this has occurred. (Well, the windings are discolored
and the smell is what clued me in to these problems.) When I put in a
replacement alternator Išm quite confident everything will look just fine.
Until next time.  

What could cause these symptoms? Twice?

Thanks!

Does the alternator use Avalanche Diodes? A bad battery wiring
connection will cause a diode to short. I'd check the terminals and
crimps.

BTW I had this problem with the double GM battery lugs, they used a
lead spacer that shrunk when it thermal cycled.

\Cheers

 

[Sparky]

If you asked in rec.autos.tech you'd get answers with less knowledge of
theory but with more knowledge of common failure modes.

THANK YOU! Hadn't crossed my mind (being the eletrickery kind of guy that I
am...)

Best day to you!

 

[Sparky]

> Do you happen to have quadruple 300 W audio channels on board?

No, mostly stock old Toyota. Only additional load is Xenon lamps. These pull
10A total which isn't much for lights...

Maybe I'll upgrade the alternator to a later-model Toyota 70A or such.

 

[Sparky]

Did you change the battery any time after the alternator was changed or is
it the same one still?

Replaced with new from NAPA auto parts, not the cheapest, but a quality one.

 

[Tom Del Rosso]

Sparky wrote:

Last year the alternator on my Toyota cooked the stator windings. I
didnšt look any further and replaced it with a rebuilt alternator &
regulator from the local parts supplier.

Now (7 or 8 months later) the replacement has failed in the same
mode. Išm suspicious. Also confused:

If you asked in rec.autos.tech you'd get answers with less knowledge of
theory but with more knowledge of common failure modes.

--

 

[Sparky]

No, ONE a shorted diode would cause huge currents in the winding
connected to that phase. Two shorted diodes on the same
phase would cause huge DC currents and blow the fusible link.

Jon

Ah. Then might be one shorted diode... Should probably upgrade alternator to
a higher-amp one that can handle the car's load more easily.

 

[Ron D.]

I'd have to agree with connections. I did, however hear of an internally corroded battery cable. I once had a corroded bulkhead connector do it.

In one case the paint shop didn;t tighten the battery cable. Could I prove it? NO!

Between the bulkhead connector and the alternator where the rotot solder joint just broke, I don't know what was more difficult. The corrosion was harder to find. The broken rotor connection gave no indication, whatsoever. The car just stopped.

 

[rickman]

On 2/16/2015 10:16 PM, Sparky wrote:

Do you happen to have quadruple 300 W audio channels on board?

No, mostly stock old Toyota. Only additional load is Xenon lamps. These pull
10A total which isn't much for lights...

Maybe I'll upgrade the alternator to a later-model Toyota 70A or such.

What is your current unit rated for 60A?

I replaced the 70A alternator in my truck when a diode opened up. It
was still working, but not enough juice to charge the battery when the
lights were on and I run the headlights all the time, lol. Nothing ever
got fried though.

What is your alternator model number? What year? Mine is a 97 T100 and
I found they changed the alternator in mid model year (around April,
IIRC). Causes a lot of confusion on what is the right model. I tried
finding a replacement diode bridge. *That* was the major change and was
incompatible between the two versions. When looking for parts be sure
to use the VIN to get the right one.

I ended up getting a used alternator and it is running ok now...
although it is in the shop for a clutch. They've ordered two so far.
The first pressure plate "collapsed" whatever that means and the springs
on the second weren't right. They are giving NAPA some hell over this
and are getting an upgraded one to put in my truck. Hope to have it soon.

--

Rick

 

[Sparky]

The battery was replaced at the same time as was the alternator: 5 months ago
(corrected from my original post). 

Measurement of battery cables: from battery cable (+) terminal to alternator
(+) terminal: 1.5 ohms. From battery cable (-) terminal to chassis: 1.5
ohms. 

Charging numbers with new alternator & 5 months old battery:
With partially (50%?) depleted battery, when the car was started and engine
revved, the new alternator output 34 amps, headlights off. With lights on
high, output was 44 amps. Charge voltage was 14.04 volts. These numbers are
within those specified in the Toyota factory manual (charge current: ł30A or
more˛; charge voltage: ł13.9-15.1˛. 

Thanks.

 

[Tauno Voipio]

On 18.2.15 09:27, Sparky wrote:

The battery was replaced at the same time as was the alternator: 5 months ago
(corrected from my original post).

Measurement of battery cables: from battery cable (+) terminal to alternator
(+) terminal: 1.5 ohms. From battery cable (-) terminal to chassis: 1.5
ohms.

Charging numbers with new alternator & 5 months old battery:
With partially (50%?) depleted battery, when the car was started and engine
revved, the new alternator output 34 amps, headlights off. With lights on
high, output was 44 amps. Charge voltage was 14.04 volts. These numbers are
within those specified in the Toyota factory manual (charge current: ł30A or
more˛; charge voltage: ł13.9-15.1˛.

Thanks.

Your measurements cannot be good, or the thing does not charge
the battery. If there were only 10 A, you'd lose 30 V in the cables.

For starting, you will need hunders of amperes, but the battery
voltage cannot put even 10 A to the grounding cable.

--

-TV

 

[Tom Del Rosso]

Sparky wrote:

The battery was replaced at the same time as was the alternator: 5
months ago (corrected from my original post).

Measurement of battery cables: from battery cable (+) terminal to
alternator (+) terminal: 1.5 ohms. From battery cable (-) terminal to
chassis: 1.5 ohms.

That resistance is too high, maybe because you measured from a bad contact
point.

 

[micky]

On Mon, 16 Feb 2015 19:31:57 -0800, Sparky <see@thesig.net> wrote:

No, ONE a shorted diode would cause huge currents in the winding
connected to that phase. Two shorted diodes on the same
phase would cause huge DC currents and blow the fusible link.

Jon

Ah. Then might be one shorted diode... Should probably upgrade alternator to
a higher-amp one that can handle the car's load more easily.

Do you have one or both old alternators? How about checking out the
diodes in them?

I try to fix everything that breaks myself. I'll let something stay
broken for years while I try to figure out how to fix it, rather than
pay someone. Of course I can't let the car stay broken for more than a
day.

When my brother gave me his car, he had a problem with a battery that
repeatedly went dead, for more than two years, ever since he bought the
car new. It came with a 2-year warranty and the dealer had replaced the
alternator, the regulator, and the battery, each of them twice, and
still the problem. Then the dealer said the warranty had expired and
wouldn't do anymore.

Annoyed, he gave me the car. It had a another bad battery by this time
and I took it to Sears. They said do you want our free 235,000 point
multi-check? I said, No, just a battery. He said, It's free. I said
okay. And in less than 5 minutes he found the problem that the dealer
couldn't find in 2 years. In my case it was a bad connection at the
starter motor with the + battery cable. He took it apart and cleaned
it**. I don't know what the problem is with yours but sometimes it
pays to pay someone. Also many people tend to spend all their time on
the big parts and not enough on the wires between them.


**I also bought a new battery, but it's cleaning it that made it work
fine, until months later, I left the headlights on all night. Jumped the
battery and ran the car an hour but it still wouldn't start the next
day. I had to crawl underneath, take the cable off, clean everything
and put it back. Until the next time I left the lights on.
Eventually I learned, even in good clothes, to just stick my arm
underneath, grab the battery cable and pull it back and forth, rotating
on the stater motor stud, once or twice, and then the car would run fine
until the next time I left the lights on. I've run down the battery by
leaving the lights on on other cars without having any endruing
problem. I don't know what made this car different, but my point is that
Sears found the problem in less than 5 minutes.

He gave me the car when he went to Viet Nam, in 1967, but the story
still applies.

 

[micky]

On Wed, 18 Feb 2015 06:58:13 -0500, micky <NONONOmisc07@bigfoot.com>
wrote:

**I also bought a new battery, but it's cleaning it that made it work
fine, until months later, I left the headlights on all night. Jumped the
battery and ran the car an hour but it still wouldn't start the next
day. I had to crawl underneath, take the cable off, clean everything
and put it back. Until the next time I left the lights on.
Eventually I learned, even in good clothes, to just stick my arm
underneath, grab the battery cable and pull it back and forth, rotating
on the starter motor stud, once or twice, and then the car would run fine
until the next time I left the lights on.

This sounds like the nut was loose that held the cable on. I'm never
quite sure how much to tighten nuts but it was pretty tight. It's
mostly that I had a lot of leverage pulling on the cable 3 and 4 inches
from the pivot point.

And the mechnanics who changed the starter twice should have known how
tight to make the nut (At least the dealer said he changed everything
twice. When I moved to the city my brother was in, 3 years later, a
year after he left the army, the dealer was out of business!)

I thought about changing the battery cable for one that might not be so
touchy, but instead I found a buzzer that buzzed if I left the
headlights on. That prevented both the ongoing problem and the first
day's dead battery. Problem solved.

Do you all think a different battery cable might have worked better?

 

[Rich.]

"Tom Del Rosso" <td005@verizon.net.invalid> wrote in message
news:mc1phr$pjk$1@dont-email.me...

Sparky wrote:
The battery was replaced at the same time as was the alternator: 5
months ago (corrected from my original post).

Measurement of battery cables: from battery cable (+) terminal to
alternator (+) terminal: 1.5 ohms. From battery cable (-) terminal to
chassis: 1.5 ohms.

That resistance is too high, maybe because you measured from a bad contact
point.

Typical meter leads have a resistance of 1.5 ohms. It's possible he did not
short the leads and zero out the meter first. If not, then the battery cable
resistance actually drops to zero.

 

[Mike]

On Wed, 18 Feb 2015 09:46:23 -0500, Rich. wrote:

> Typical meter leads have a resistance of 1.5 ohms. ...

I hope not a meter that claims to measure currents of (say) 10 amps!

Mike.