On Thu, 13 Nov 1997 18:52:36 +0000 Robert Allen <boballen@sky.net>
writes:
>..... In the 'C' shop manual it says the standard dizzy consumes 3.9
amps "Ignition On: Standing" and 1.4 amps at 2,000 rpm. So I was figuring
that there would be less of a current load on the points at higher rpm.
>
>So ya don't think so? Is 'standing' when the motor ain't turnin' and the
other 2.5 amps is used to heat the coil? I _know_ the coil can get pretty
hot if you leave the ignition on without starting the car...
"Ignition On Standing" means not running. When the points are closed
continuously the coil draws a pretty high current, so high in fact that
it can overheat and self destruct if left on long enough. When the
engine is running the points are closed less than half the time, and when
the points are open the coil is drawing no current and generating no
heat.
Take the mathematical average of the current flow(s) when running,
assuming the points are closed 40% of the time. (3.9a x 0.4 + 0.0a x
0.6) = 1.56a That's pretty close to the 1.4 amps noted in your book.
If you measure the current when the engine is running with an analog
meter, you may see the 1.4 amps, which is the average current flow
driving the needle on the meter. If you're using a digital meter, the
numbers may keep jumping all over the place, depending on the time in the
contact points switching cycle when the meter is doing the sampling.
(The same aplies to a voltage reading). The 1.4 amps should be fairly
constant over the full speed range of the engine.
Barney Gaylord
1958 MGA with an attitude
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