[DeTomaso] Alternator blues....

Thomas Törnblom tipo874 at gmail.com
Mon Oct 3 15:50:41 EDT 2016


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
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