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@home.se> To: tipo874@gmail.com Cc: MikeLDrew@aol.com; detomaso@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@gmail.com]   Sent: 3/10/2016 9:49:41 PM   To: MikeLDrew@aol.com   Cc: detomaso@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@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@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@jpl.nasa.gov   >>   >> From: DeTomaso <[2]detomaso-bounces@server.detomasolist.com> on   behalf   >> of Julian Kift <[3]julian_kift@hotmail.com>   >> Date: Monday, October 3, 2016 6:57 AM   >> To: "[4]MikeLDrew@aol.com" <[5]MikeLDrew@aol.com>,   >> "[6]detomaso@server.detomasolist.com"   >> <[7]detomaso@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@server.detomasolist.com> on   behalf   >> of Mike Drew via DeTomaso <[9]detomaso@server.detomasolist.com>   >> Sent: Sunday, October 2, 2016 9:11 PM   >> To: [10]detomaso@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@jpl.nasa.gov   >> 2. mailto:detomaso-bounces@server.detomasolist.com   >> 3. mailto:julian_kift@hotmail.com   >> 4. mailto:MikeLDrew@aol.com   >> 5. mailto:MikeLDrew@aol.com   >> 6. mailto:detomaso@server.detomasolist.com   >> 7. mailto:detomaso@server.detomasolist.com   >> 8. mailto:detomaso-bounces@server.detomasolist.com   >> 9. mailto:detomaso@server.detomasolist.com   >> 10. mailto:detomaso@server.detomasolist.com   >> _______________________________________________   >>   >>   >> Detomaso Email List is not managed by POCA   >> Posted emails must not exceed 1.5 Megabytes   >> DeTomaso mailing list   >> DeTomaso@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@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@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@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. 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@home.se> To: tipo874@gmail.com Cc: MikeLDrew@aol.com; detomaso@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 [[1]tipo874@gmail.com] Sent: 3/10/2016 9:49:41 PM To: [2]MikeLDrew@aol.com Cc: [3]detomaso@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 <[4]detomaso@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)" <[5]terry.himes@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][6]thimes@jpl.nasa.gov >> >> From: DeTomaso <[2][7]detomaso-bounces@server.detomasolist.com> on behalf >> of Julian Kift <[3][8]julian_kift@hotmail.com> >> Date: Monday, October 3, 2016 6:57 AM >> To: "[4][9]MikeLDrew@aol.com" <[5][10]MikeLDrew@aol.com>, >> "[6][11]detomaso@server.detomasolist.com" >> <[7][12]detomaso@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][13]detomaso-bounces@server.detomasolist.com> on behalf >> of Mike Drew via DeTomaso <[9][14]detomaso@server.detomasolist.com> >> Sent: Sunday, October 2, 2016 9:11 PM >> To: [10][15]detomaso@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:[16]thimes@jpl.nasa.gov >> 2. mailto:[17]detomaso-bounces@server.detomasolist.com >> 3. mailto:[18]julian_kift@hotmail.com >> 4. mailto:[19]MikeLDrew@aol.com >> 5. mailto:[20]MikeLDrew@aol.com >> 6. mailto:[21]detomaso@server.detomasolist.com >> 7. mailto:[22]detomaso@server.detomasolist.com >> 8. mailto:[23]detomaso-bounces@server.detomasolist.com >> 9. mailto:[24]detomaso@server.detomasolist.com >> 10. mailto:[25]detomaso@server.detomasolist.com >> _______________________________________________ >> >> >> Detomaso Email List is not managed by POCA >> Posted emails must not exceed 1.5 Megabytes >> DeTomaso mailing list >> [26]DeTomaso@server.detomasolist.com >> [27]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 > [28]DeTomaso@server.detomasolist.com > [29]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 [30]DeTomaso@server.detomasolist.com [31]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 [32]DeTomaso@server.detomasolist.com [33]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. References 1. mailto:tipo874@gmail.com 2. mailto:MikeLDrew@aol.com 3. mailto:detomaso@server.detomasolist.com 4. mailto:detomaso@server.detomasolist.com 5. mailto:terry.himes@jpl.nasa.gov 6. mailto:thimes@jpl.nasa.gov 7. mailto:detomaso-bounces@server.detomasolist.com 8. mailto:julian_kift@hotmail.com 9. mailto:MikeLDrew@aol.com 10. mailto:MikeLDrew@aol.com 11. mailto:detomaso@server.detomasolist.com 12. mailto:detomaso@server.detomasolist.com 13. mailto:detomaso-bounces@server.detomasolist.com 14. mailto:detomaso@server.detomasolist.com 15. mailto:detomaso@server.detomasolist.com 16. mailto:thimes@jpl.nasa.gov 17. mailto:detomaso-bounces@server.detomasolist.com 18. mailto:julian_kift@hotmail.com 19. mailto:MikeLDrew@aol.com 20. mailto:MikeLDrew@aol.com 21. mailto:detomaso@server.detomasolist.com 22. mailto:detomaso@server.detomasolist.com 23. mailto:detomaso-bounces@server.detomasolist.com 24. mailto:detomaso@server.detomasolist.com 25. mailto:detomaso@server.detomasolist.com 26. mailto:DeTomaso@server.detomasolist.com 27. http://server.detomasolist.com/mailman/listinfo/detomaso 28. mailto:DeTomaso@server.detomasolist.com 29. http://server.detomasolist.com/mailman/listinfo/detomaso 30. mailto:DeTomaso@server.detomasolist.com 31. http://server.detomasolist.com/mailman/listinfo/detomaso 32. mailto:DeTomaso@server.detomasolist.com 33. http://server.detomasolist.com/mailman/listinfo/detomaso