Randall wrote:
>>Randall wrote:
>>
>>
>>
>>>>Here's a $64 question - why did the rpm's increase as the coil voltage
>>>>decrease?
>>>
>>>
>>>Beats me.
>
>
> Michael D. Porter replied :
>
>
>>Could be that the residual current is not enough to do anything but
>>marginally energize the alternator field, so the load on the engine
>>from the alternator is much smaller
>
>
> I'm fairly certain that's not the case, Michael. The same voltage that is
> powering the ignition through the resistor is also powering the alternator
> field through the regulator. Remember he measured 10.5 volts at the coil,
> which is plenty to power the alternator field to better than 50% of capacity
> at least. And since that was after the 5 ohm resistor, the voltage at the
> regulator is probably even higher (like still 14.4).
Well, not schematically seeing the way the resistor works in a
circuit with an electronic ignition, my only guess about this is
that some sort of loop circuit is created by the introduction of the
resistor.
I've run into something similar to this before--on buses. We had a
problem with some buses not shutting down when the battery
disconnect switches were thrown off, because the ignition was still
on. That created a loop where residual magnetism in the alternator
provided just enough current which looped through the run circuit to
run the ECM and the injectors. There wasn't enough current to charge
the batteries, were they connected, but was enough to keep those
circuits on. The only way to solve the problem was to mechanically
interrupt field input power from the run circuit.
I would say that something similar is happening in this case, since
if the alternator were providing sufficient current to run the field
enough to load the engine, that would compensate for an additional
load on the regulator wire circuit, which the poster says it does
not--when the heater is turned on, the car dies. The alternator
obviously isn't compensating for the internal voltage drop in the
regulator when the heater turns on.
If there's a capacitor _somewhere_ in the circuit providing just
enough current to the field controller, that might keep it just
barely going through some sort of loop which recharges the capacitor.
As I say, without seeing how it's wired, it's just a guess.
Cheers.
--
Michael D. Porter
Roswell, NM
Never let anyone drive you crazy when you know it's within walking
distance.
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