The ignition warning light acts as a pair of balance scales with one side
connected to the battery and the other to the field coils, which are
isolated from the battery by diodes. Under normal circumstances when the
alternator is charging the battery it will also be 'charging' the field
coils with the same voltage, so the ignition warning light will have the
same voltage both sides and hence the scales will be balanced, i.e. no
light. If anything causes the voltage to be imbalanced i.e ignition on but
alternator not charging, or ignition off but alternator charging (i.e. when
the car is rolling and in gear but the ignition is off) or one or more
diodes are open or short the lamp will light to varying degrees, and if it's
diodes, usually light more as the load increases
Your problem could be something as simple as one side of the ignition
warning lamp grounding from time to time, as the lamp holder is unique in
that it must be insulated from the speedo casing. Unplug it from the back
of the speedo and see if it makes any difference, it should still work in
the normal way.
>When the battery gets
>to 14 volts, ( a minute or two) the light comes on, and I'll see no
current
>flow on the amp meter
This bit needs clarification. Do you mean that the ignition light gradually
comes on and the current flow gradually reduces to nothing (this is normal),
or after a minute or two the light suddenly comes on the the current flow
suddenly ceases? This is not normal, and I would expect it to be
accompanied by a drop in voltage. You need to measure the voltage to ground
on both sides of the lamp while it is on, this will tell you whether the
reduced (or excess) voltage is coming from the ignition side or the
alternator side
> Watching the Volt Meter, I can see a rhythmic pulsing of the voltage.
>It's only a 1/2 a volt or so drop, but is rhythmic and doesn't seem to be
>related to engine RPM. I'm assuming this pulse is the Fuel pump being
>energized.
There is no way that the fuel pump should affect the voltage reading,
particularly when charging, by this much. If it is the pump then either the
pump is drawing way to much current (possible, but not very likely) or you
have some very poor connections. There should be a relation to rpm, since
more rpm requires more fuel i.e more frequent ticks of the pump, albeit with
a slight time delay.
PaulH.
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