[DeTomaso] Alternator blues....

Mike Drew MikeLDrew at aol.com
Mon Oct 3 12:00:18 EDT 2016


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. 


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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