[DeTomaso] Alternator blues....
JEFFREY COBB
jeffcobb1 at me.com
Mon Oct 3 07:13:41 EDT 2016
Good morning Mike,
High ohm engine ground strap connections will cause spastic and damaging alternator function.
If it charges now then use a hand held load meter;
-1-set idle-hold at 1,500 and note volts + amps at both battery post at no load, now load the meter and note,
-2-Then from batt positive post to closest frame ground, loading and noting again, a six second 100 amp load will smoke out the weak connection,
-3-Then from alternator output post to engine block, repeat above no and load test,
-4-repeat from alt output to frame ground, repeat above no and load test,
-5-now place load meter or test light from engine to frame ground and find voltage or light,
1 and 3 will be closely identical, though 3 slightly less due to wire distance ohm reduction, reference values that you can base the alt function and amp meter realities.
2 and 4 will help you find electrical resistance.
If all above 8 test give pretty much same values within a .3 volt and 5 amp variance then you need to find flaw elsewhere. Sometimes a 10 second 100 amp load test at 3,000 may break your hidden problem, try and see if above 8 don't point to issue.
If it does not charge then use a large battery charger and load both battery post then repeat and charge alt stud and engine ground, you may find resistance.
Also an extra large woven ground strap never hurts!
33 years ago the Baton Rouge Volvo dealer sold me 6 defective alternators in a row for the same customer. I was the largest Volvo repair shop in town and also was paid my said dealer to do warranty work for them as they were overloaded. The 7th one worked, the owner was scamming his dealership and was putting new-defective-warrantied alternators back in stock so to make more money to finance his hydroplane racing. Of course I was the largest buyer of Volvo parts so I got stung and customer was pissed beyond belief. Year or so later when owner was busted, jailed and dealer closed, his son brought me as a guilt gift a new Volvo cylinder head in crate and other parts so to make amends.
Poo-poo occurs.
Back in March prepping for Amelia, I noticed where my Mangusta had electrical burning marks on the alloy around the large bell housing bolt washer interfaces, WTF???, we found the bolts not to be as tight as they should have been.
So my alternator engine ground was trying and having a difficult time getting back to the true body-battery ground and left burning-jumping marks on the bell housing. Now all is fine and battery cable temps are cooler.
Good luck,
Jeff
Jeff Cobb- I pad
W-225-343-7525
C-225-907-4514
On Oct 2, 2016, at 11:11 PM, Mike Drew via DeTomaso <detomaso at server.detomasolist.com> wrote:
> 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
> _______________________________________________
>
>
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-------------- next part --------------
Good morning Mike,
High ohm engine ground strap connections will cause spastic and
damaging alternator function.
If it charges now then use a hand held load meter;
-1-set idle-hold at 1,500 and note volts + amps at both battery post at
no load, now load the meter and note,
-2-Then from batt positive post to closest frame ground, loading and
noting again, a six second 100 amp load will smoke out the weak
connection,
-3-Then from alternator output post to engine block, repeat above no
and load test,
-4-repeat from alt output to frame ground, repeat above no and load
test,
-5-now place load meter or test light from engine to frame ground and
find voltage or light,
1 and 3 will be closely identical, though 3 slightly less due to wire
distance ohm reduction, reference values that you can base the alt
function and amp meter realities.
2 and 4 will help you find electrical resistance.
If all above 8 test give pretty much same values within a .3 volt and 5
amp variance then you need to find flaw elsewhere. Sometimes a 10
second 100 amp load test at 3,000 may break your hidden problem, try
and see if above 8 don't point to issue.
If it does not charge then use a large battery charger and load both
battery post then repeat and charge alt stud and engine ground, you may
find resistance.
Also an extra large woven ground strap never hurts!
33 years ago the Baton Rouge Volvo dealer sold me 6 defective
alternators in a row for the same customer. I was the largest Volvo
repair shop in town and also was paid my said dealer to do warranty
work for them as they were overloaded. The 7th one worked, the owner
was scamming his dealership and was putting new-defective-warrantied
alternators back in stock so to make more money to finance his
hydroplane racing. Of course I was the largest buyer of Volvo parts so
I got stung and customer was pissed beyond belief. Year or so later
when owner was busted, jailed and dealer closed, his son brought me as
a guilt gift a new Volvo cylinder head in crate and other parts so to
make amends.
Poo-poo occurs.
Back in March prepping for Amelia, I noticed where my Mangusta had
electrical burning marks on the alloy around the large bell housing
bolt washer interfaces, WTF???, we found the bolts not to be as tight
as they should have been.
So my alternator engine ground was trying and having a difficult time
getting back to the true body-battery ground and left burning-jumping
marks on the bell housing. Now all is fine and battery cable temps are
cooler.
Good luck,
Jeff
Jeff Cobb- I pad
W-225-343-7525
C-225-907-4514
On Oct 2, 2016, at 11:11 PM, Mike Drew via DeTomaso
<[1]detomaso at server.detomasolist.com> wrote:
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
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