[DeTomaso] Alternator blues....

Tomas Gunnarsson guson at home.se
Fri Oct 7 03:29:21 EDT 2016


The AC Delco 10si alternator has nine internal rectifier diodes, see
attached pics. The main six diode rectifier bridge is top middle. The
triple diode that powers the regulator is to the left of the ball
bearing. This triple diode is also what turns off the alternator lamp.
If you hook up a load between lamp terminal and ground this bridge will
provide power to the load, something it's not designed to do. The result
will be burnt out diodes in the diode trio and a loss of power to the
regulator which in turn leads to loss of alternator output. Like you I
think that the problem is the regulator but the question is why it keeps
breaking.
 
Tomas

<-----Ursprungligt Meddelande----->

 	  	 From: Guido deTomaso [guido_detomaso at prodigy.net]
Sent: 6/10/2016 6:01:07 PM
To: guson at home.se;tipo874 at gmail.com
Cc: MikeLDrew at aol.com;detomaso at server.detomasolist.com
Subject: Re: [DeTomaso] Alternator blues.... 


I'm lost ... the rectifier diodes, typically six, each transit roughly
1/3 of the alternators output.  Collectively they transmit all the
output power.  Any loads added anywhere tax the diodes. 
OTOH, certain cars I'm aware of run many loads through the lamp circuit,
bulb test in the example I'm familiar with, and some/many/most
alternator voltage regulators can't handle the current.  These require a
special voltage regulator. 
Unlikely the root cause of the problem at hand ... my money is on bad
regulator unfortunately inside the GM alternator not conveniently remote
mounted. 
Or so it seems to me, I could be wrong. 
GD 


From: Tomas Gunnarsson <guson at home.se> 
To: tipo874 at gmail.com 
Cc: MikeLDrew at aol.com; detomaso at server.detomasolist.com 
Sent: Wednesday, October 5, 2016 11:55 PM 
Subject: Re: [DeTomaso] Alternator blues.... 

  If the marginal connection is between battery and ammeter it will 
  fluctuate between zero and charge. If it's between alternator and 
  ammeter it will fluctuate between charge and discharge. Right Thomas? 
  Another thought: Have you by accident hooked anything up to the lamp 
  post on the alternator (or the wire going between post and dashboard 
  lamp) that's using significant power? That pin will provide power when
running but the rectifier diodes inside will not be up for the task and 
  burn out in short time. Just a thought as you've been going through 
  alternators at high pace. I'd like to disconnect the lamp wire from
the 
  alternator with the engine running and see what happens. Note that the
sense wire will have to stay connected if you have one. 



  Tomas 
  <-----Ursprungligt Meddelande-----> 

      From: Thomas Toernblom [tipo874 at gmail.com] 
  Sent: 3/10/2016 9:49:41 PM 
  To: MikeLDrew at aol.com 
  Cc: detomaso at server.detomasolist.com 
  Subject: Re: [DeTomaso] Alternator blues.... 
  Check the fat wire from B+ (or what it is called on the alt) to the 
  ammeter. If there is a marginal connection there the voltage can 
  fluctuate wildly and possibly kill semiconductors in the alt. 
  > 3 okt. 2016 kl. 18:00 skrev Mike Drew via DeTomaso 
  <detomaso at server.detomasolist.com>: 
  > 
  > All, 
  > 
  > Further to my original inquiry, I failed to mention that this is a
GM 
  alternator with built-in regulator, running in the stock three-wire 
  configuration. Normally it works normally--shows a somewhat strong 
  charge for a short time after engine start, coming back down to slight
charge when battery is 'full' again, with slight discharge at idle when 
  fans, lights etc are on. 
  > 
  > When it starts acting up, initially the needle bounces erratically 
  over a small range between slight charge and slight discharge. After a
few minutes of that, it goes into greater discharge mode as it quits 
  completely. 
  > 
  > Mike 
  > 
  > Sent from my iPhone 
  > 
  >> On Oct 3, 2016, at 8:15, "Himes, Terry (397C)" 
  <terry.himes at jpl.nasa.gov> wrote: 
  >> 
  >> Ditto. I put in 2 rebuilt units and they both failed. Finally
bought 
  >> a new one. 
  >> No problem since. 
  >> 
  >> "A Purple Heart proves you were smart enough to hatch a plan, 
  >> 
  >> stupid enough to try it and lucky enough to survive!" 
  >> 
  >> Terry W. Himes 
  >> 
  >> JPL Jet Propulsion Laboratory 
  >> 
  >> Dawn Spacecraft Team 
  >> 
  >> Rosetta Sequence Team Lead 
  >> 
  >> Phone: (818) 393-6261 
  >> 
  >> Cell: (818) 653-8213 
  >> 
  >> Fax: (818) 393-3147 
  >> 
  >> [1]thimes at jpl.nasa.gov 
  >> 
  >> From: DeTomaso <[2]detomaso-bounces at server.detomasolist.com> on 
  behalf 
  >> of Julian Kift <[3]julian_kift at hotmail.com> 
  >> Date: Monday, October 3, 2016 6:57 AM 
  >> To: "[4]MikeLDrew at aol.com" <[5]MikeLDrew at aol.com>, 
  >> "[6]detomaso at server.detomasolist.com" 
  >> <[7]detomaso at server.detomasolist.com> 
  >> Subject: Re: [DeTomaso] Alternator blues.... 
  >> 
  >> Mike, 
  >> I hate chasing these type of electrical problems, but here's some 
  >> thoughts; 
  >> i) Battery going bad (how old is it?), requiring the alternator to 
  have 
  >> to constantly charge 
  >> ii) Some alternator re builders are notorious for units failing, 
  over a 
  >> 50% failure rate is not uncommon. I had a similar issue with my 
  GT40; 
  >> on the third alternator we switched to a higher amp 'new' unit and 
  >> never had a problem since. 
  >> iii) It could also be an intermittent short or bad ground 
  >> Julian 
  >> ________________________________ 
  >> From: DeTomaso <[8]detomaso-bounces at server.detomasolist.com> on 
  behalf 
  >> of Mike Drew via DeTomaso <[9]detomaso at server.detomasolist.com> 
  >> Sent: Sunday, October 2, 2016 9:11 PM 
  >> To: [10]detomaso at server.detomasolist.com 
  >> Subject: [DeTomaso] Alternator blues.... 
  >> Hi guys, 
  >> Just got home from a terrific weekend in the Sierra foothills; 24 
  >> Panteras 
  >> (of the 36 scheduled) took part in the Niello concours at Serrano. 
  It 
  >> heaved down with rain for a very brief period, but that rain then 
  >> turned to snow 
  >> which kept the large Reno/Tahoe contingent from braving the summit.
>> Still, a great time was had by all who attended, and we drove home 
  in 
  >> splendid 
  >> sunshine. 
  >> We were driving in Lori's Pantera, which has a flat firewall kit
and 
  >> uses a 
  >> GM alternator with built-in regulator. She drove the car to Vegas 
  >> this 
  >> spring, and the alternator failed while we were there. At first it 
  >> started 
  >> acting erratic, with the amp needle bouncing around, and then 
  finally 
  >> it quit 
  >> and just showed a partial discharge. Testing at the battery
revealed 
  >> it 
  >> was doing nothing at that point. We replaced it with another one, 
  >> which did 
  >> exactly the same thing and failed about 50 miles from home. 
  >> We replaced THAT one, and the third one has worked fine until
today. 
  >> But 
  >> it probably only has about 250 miles on it or so. On the way home, 
  >> once 
  >> again, I noticed the ammeter needle behaving erratically, then it 
  quit 
  >> and 
  >> showed partial discharge for many miles, then briefly came back to 
  life 
  >> and 
  >> showed a very strong charge (since we had been running on battery 
  power 
  >> for 
  >> awhile), then discharged again. 
  >> Methinks the problem is not simply that alternators are failing,
but 
  >> rather 
  >> that there is some sort of fault in the electrical system. As 
  >> electrons 
  >> are far from my strong suit, I hesitate to start diving it to it 
  >> blindly. 
  >> What say all of you? 
  >> FWIW we've got a spare alternator we will be installing tomorrow, 
  which 
  >> almost assuredly will work just fine...for awhile anyway???? 
  >> Mike 
  >> 
  >> References 
  >> 
  >> 1. mailto:thimes at jpl.nasa.gov 
  >> 2. mailto:detomaso-bounces at server.detomasolist.com 
  >> 3. mailto:julian_kift at hotmail.com 
  >> 4. mailto:MikeLDrew at aol.com 
  >> 5. mailto:MikeLDrew at aol.com 
  >> 6. mailto:detomaso at server.detomasolist.com 
  >> 7. mailto:detomaso at server.detomasolist.com 
  >> 8. mailto:detomaso-bounces at server.detomasolist.com 
  >> 9. mailto:detomaso at server.detomasolist.com 
  >> 10. mailto:detomaso at server.detomasolist.com 
  >> _______________________________________________ 
  >> 
  >> 
  >> Detomaso Email List is not managed by POCA 
  >> Posted emails must not exceed 1.5 Megabytes 
  >> DeTomaso mailing list 
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  >> http://server.detomasolist.com/mailman/listinfo/detomaso 
  >> 
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  >> 
  >> Members who post to this list grant license to the list to forward 
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list. They also grant the list owner permission to maintain an archive 
  or approve the archiving of list messages. 
  > _______________________________________________ 
  > 
  > 
  > Detomaso Email List is not managed by POCA 
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  > DeTomaso mailing list 
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  > http://server.detomasolist.com/mailman/listinfo/detomaso 
  > 
  > To manage your subscription (change email address, unsubscribe,
etc.) 
  use the links above. 
  > 
  > Members who post to this list grant license to the list to forward 
  any message posted here to all past, current, or future members of the
list. They also grant the list owner permission to maintain an archive 
  or approve the archiving of list messages. 
  _______________________________________________ 
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  . 

_______________________________________________ 


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-------------- next part --------------
   The AC Delco 10si alternator has nine internal rectifier diodes, see
   attached pics. The main six diode rectifier bridge is top middle. The
   triple diode that powers the regulator is to the left of the ball
   bearing. This triple diode is also what turns off the alternator lamp.
   If you hook up a load between lamp terminal and ground this bridge will
   provide power to the load, something it's not designed to do. The
   result will be burnt out diodes in the diode trio and a loss of power
   to the regulator which in turn leads to loss of alternator output. Like
   you I think that the problem is the regulator but the question is why
   it keeps breaking.

   Tomas
   <-----Ursprungligt Meddelande----->
       From: Guido deTomaso [guido_detomaso at prodigy.net]
   Sent: 6/10/2016 6:01:07 PM
   To: guson at home.se;tipo874 at gmail.com
   Cc: MikeLDrew at aol.com;detomaso at server.detomasolist.com
   Subject: Re: [DeTomaso] Alternator blues....
   I'm lost ... the rectifier diodes, typically six, each transit roughly
   1/3 of the alternators output.  Collectively they transmit all the
   output power.  Any loads added anywhere tax the diodes.
   OTOH, certain cars I'm aware of run many loads through the lamp
   circuit, bulb test in the example I'm familiar with, and some/many/most
   alternator voltage regulators can't handle the current.  These require
   a special voltage regulator.
   Unlikely the root cause of the problem at hand ... my money is on bad
   regulator unfortunately inside the GM alternator not conveniently
   remote mounted.
   Or so it seems to me, I could be wrong.
   GD
   From: Tomas Gunnarsson <guson at home.se>
   To: tipo874 at gmail.com
   Cc: MikeLDrew at aol.com; detomaso at server.detomasolist.com
   Sent: Wednesday, October 5, 2016 11:55 PM
   Subject: Re: [DeTomaso] Alternator blues....
     If the marginal connection is between battery and ammeter it will
     fluctuate between zero and charge. If it's between alternator and
     ammeter it will fluctuate between charge and discharge. Right Thomas?
     Another thought: Have you by accident hooked anything up to the lamp
     post on the alternator (or the wire going between post and dashboard
     lamp) that's using significant power? That pin will provide power
   when
     running but the rectifier diodes inside will not be up for the task
   and
     burn out in short time. Just a thought as you've been going through
     alternators at high pace. I'd like to disconnect the lamp wire from
   the
     alternator with the engine running and see what happens. Note that
   the
     sense wire will have to stay connected if you have one.
     Tomas
     <-----Ursprungligt Meddelande----->
         From: Thomas Toernblom [tipo874 at gmail.com]
     Sent: 3/10/2016 9:49:41 PM
     To: MikeLDrew at aol.com
     Cc: detomaso at server.detomasolist.com
     Subject: Re: [DeTomaso] Alternator blues....
     Check the fat wire from B+ (or what it is called on the alt) to the
     ammeter. If there is a marginal connection there the voltage can
     fluctuate wildly and possibly kill semiconductors in the alt.
     > 3 okt. 2016 kl. 18:00 skrev Mike Drew via DeTomaso
     <detomaso at server.detomasolist.com>:
     >
     > All,
     >
     > Further to my original inquiry, I failed to mention that this is a
   GM
     alternator with built-in regulator, running in the stock three-wire
     configuration. Normally it works normally--shows a somewhat strong
     charge for a short time after engine start, coming back down to
   slight
     charge when battery is 'full' again, with slight discharge at idle
   when
     fans, lights etc are on.
     >
     > When it starts acting up, initially the needle bounces erratically
     over a small range between slight charge and slight discharge. After
   a
     few minutes of that, it goes into greater discharge mode as it quits
     completely.
     >
     > Mike
     >
     > Sent from my iPhone
     >
     >> On Oct 3, 2016, at 8:15, "Himes, Terry (397C)"
     <terry.himes at jpl.nasa.gov> wrote:
     >>
     >> Ditto. I put in 2 rebuilt units and they both failed. Finally
   bought
     >> a new one.
     >> No problem since.
     >>
     >> "A Purple Heart proves you were smart enough to hatch a plan,
     >>
     >> stupid enough to try it and lucky enough to survive!"
     >>
     >> Terry W. Himes
     >>
     >> JPL Jet Propulsion Laboratory
     >>
     >> Dawn Spacecraft Team
     >>
     >> Rosetta Sequence Team Lead
     >>
     >> Phone: (818) 393-6261
     >>
     >> Cell: (818) 653-8213
     >>
     >> Fax: (818) 393-3147
     >>
     >> [1]thimes at jpl.nasa.gov
     >>
     >> From: DeTomaso <[2]detomaso-bounces at server.detomasolist.com> on
     behalf
     >> of Julian Kift <[3]julian_kift at hotmail.com>
     >> Date: Monday, October 3, 2016 6:57 AM
     >> To: "[4]MikeLDrew at aol.com" <[5]MikeLDrew at aol.com>,
     >> "[6]detomaso at server.detomasolist.com"
     >> <[7]detomaso at server.detomasolist.com>
     >> Subject: Re: [DeTomaso] Alternator blues....
     >>
     >> Mike,
     >> I hate chasing these type of electrical problems, but here's some
     >> thoughts;
     >> i) Battery going bad (how old is it?), requiring the alternator to
     have
     >> to constantly charge
     >> ii) Some alternator re builders are notorious for units failing,
     over a
     >> 50% failure rate is not uncommon. I had a similar issue with my
     GT40;
     >> on the third alternator we switched to a higher amp 'new' unit and
     >> never had a problem since.
     >> iii) It could also be an intermittent short or bad ground
     >> Julian
     >> ________________________________
     >> From: DeTomaso <[8]detomaso-bounces at server.detomasolist.com> on
     behalf
     >> of Mike Drew via DeTomaso <[9]detomaso at server.detomasolist.com>
     >> Sent: Sunday, October 2, 2016 9:11 PM
     >> To: [10]detomaso at server.detomasolist.com
     >> Subject: [DeTomaso] Alternator blues....
     >> Hi guys,
     >> Just got home from a terrific weekend in the Sierra foothills; 24
     >> Panteras
     >> (of the 36 scheduled) took part in the Niello concours at Serrano.
     It
     >> heaved down with rain for a very brief period, but that rain then
     >> turned to snow
     >> which kept the large Reno/Tahoe contingent from braving the
   summit.
     >> Still, a great time was had by all who attended, and we drove home
     in
     >> splendid
     >> sunshine.
     >> We were driving in Lori's Pantera, which has a flat firewall kit
   and
     >> uses a
     >> GM alternator with built-in regulator. She drove the car to Vegas
     >> this
     >> spring, and the alternator failed while we were there. At first it
     >> started
     >> acting erratic, with the amp needle bouncing around, and then
     finally
     >> it quit
     >> and just showed a partial discharge. Testing at the battery
   revealed
     >> it
     >> was doing nothing at that point. We replaced it with another one,
     >> which did
     >> exactly the same thing and failed about 50 miles from home.
     >> We replaced THAT one, and the third one has worked fine until
   today.
     >> But
     >> it probably only has about 250 miles on it or so. On the way home,
     >> once
     >> again, I noticed the ammeter needle behaving erratically, then it
     quit
     >> and
     >> showed partial discharge for many miles, then briefly came back to
     life
     >> and
     >> showed a very strong charge (since we had been running on battery
     power
     >> for
     >> awhile), then discharged again.
     >> Methinks the problem is not simply that alternators are failing,
   but
     >> rather
     >> that there is some sort of fault in the electrical system. As
     >> electrons
     >> are far from my strong suit, I hesitate to start diving it to it
     >> blindly.
     >> What say all of you?
     >> FWIW we've got a spare alternator we will be installing tomorrow,
     which
     >> almost assuredly will work just fine...for awhile anyway????
     >> Mike
     >>
     >> References
     >>
     >> 1. mailto:thimes at jpl.nasa.gov
     >> 2. mailto:detomaso-bounces at server.detomasolist.com
     >> 3. mailto:julian_kift at hotmail.com
     >> 4. mailto:MikeLDrew at aol.com
     >> 5. mailto:MikeLDrew at aol.com
     >> 6. mailto:detomaso at server.detomasolist.com
     >> 7. mailto:detomaso at server.detomasolist.com
     >> 8. mailto:detomaso-bounces at server.detomasolist.com
     >> 9. mailto:detomaso at server.detomasolist.com
     >> 10. mailto:detomaso at server.detomasolist.com
     >> _______________________________________________
     >>
     >>
     >> Detomaso Email List is not managed by POCA
     >> Posted emails must not exceed 1.5 Megabytes
     >> DeTomaso mailing list
     >> DeTomaso at server.detomasolist.com
     >> http://server.detomasolist.com/mailman/listinfo/detomaso
     >>
     >> To manage your subscription (change email address, unsubscribe,
     etc.) use the links above.
     >>
     >> Members who post to this list grant license to the list to forward
     any message posted here to all past, current, or future members of
   the
     list. They also grant the list owner permission to maintain an
   archive
     or approve the archiving of list messages.
     > _______________________________________________
     >
     >
     > Detomaso Email List is not managed by POCA
     > Posted emails must not exceed 1.5 Megabytes
     > DeTomaso mailing list
     > DeTomaso at server.detomasolist.com
     > http://server.detomasolist.com/mailman/listinfo/detomaso
     >
     > To manage your subscription (change email address, unsubscribe,
   etc.)
     use the links above.
     >
     > Members who post to this list grant license to the list to forward
     any message posted here to all past, current, or future members of
   the
     list. They also grant the list owner permission to maintain an
   archive
     or approve the archiving of list messages.
     _______________________________________________
     Detomaso Email List is not managed by POCA
     Posted emails must not exceed 1.5 Megabytes
     DeTomaso mailing list
     DeTomaso at server.detomasolist.com
     http://server.detomasolist.com/mailman/listinfo/detomaso
     To manage your subscription (change email address, unsubscribe, etc.)
     use the links above.
     Members who post to this list grant license to the list to forward
   any
     message posted here to all past, current, or future members of the
     list. They also grant the list owner permission to maintain an
   archive
     or approve the archiving of list messages.
     .
   _______________________________________________
   Detomaso Email List is not managed by POCA
   Posted emails must not exceed 1.5 Megabytes
   DeTomaso mailing list
   DeTomaso at server.detomasolist.com
   http://server.detomasolist.com/mailman/listinfo/detomaso
   To manage your subscription (change email address, unsubscribe, etc.)
   use the links above.
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