[DeTomaso] Generator light

[Thomas Tornblom]

The indicator lamp is connected between the alternator and switched 
power and indicates the voltage difference between the alternator and 
the switched circuit. With the ignition on, engine off, the alternator 
is at 0V, the switched circuit is at battery voltage, thus there is a 
nominal 12V over the lamp, and it is lit. With the ignition on, engine 
running, both voltages are nominally at 12V, thus no voltage across the 
lamp, and it is off.

If, for some reason, the alternator voltage is higher than the switched 
voltage, the lamp will also be lit, likely very dim as the voltage 
difference will likely be low. This can happen with marginal connections 
on the switched side and high current draw, like headlights on, fans 
running full blast.

As Mike says, the ammeter indicates if the battery is being charged or 
discharged, as long as there are no consumers wired directly to the 
battery, in which case that current draw will incorrectly be shown as a 
charging.

Thomas


Den 2017-07-20 kl. 18:26, skrev Mike Drew via DeTomaso:
> Tom,
> 
> Genuine experts will answer later; in the meantime I will weigh in as I have been dealing with this issue in Lori's Pantera for some time.
> 
> What is the ammeter indicating when the battery light comes on? It likely shows a discharge.
> 
> If the light is flickering, the ammeter will probably be shifting back and forth between charge and discharge.
> 
> The fault is almost assuredly not with the battery, but rather with the charging system or connections. Lori had a number of unrelated malfunctions including the alternator being loose in the mounting bracket and shaking itself to death, but ultimately we discovered the main wire leading from the alternator to the fusebox had been cut and spliced by a prior owner, and was arcing against the body, creating an intermittent short circuit.
> 
> Mike
> 
> Sent from my iPad
> 
>> On Jul 20, 2017, at 08:32, Tom Cabanski <tcabanski at tencom.com> wrote:
>>
>>    Since there was a bit of discussion on batteries and starting the car I
>>    wanted get some
>>
>>    ideas on my generator light that flickers on & off.
>>
>>
>>    I believe my battery is bad as I check the voltage across it while the
>>    car was running and it showed 13.9 to 14.2 volts,
>>
>>    Yet it died on me and I had to jump it. Charging the battery now has it
>>    starting fine at this time.
>>
>>
>>    Would a battery going bad cause the light to go on or is there
>>    something else that is a problem?
>>
>>    Tom
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-- 
Real life:   Thomas Törnblom             Email:    thomas at hax.se
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