>I was checking out my M51 last fall and as I recall there was about 5
>volts between the coil hot terminal and ground when the points were
>closed. So that sounds about right to me.
>
Not knowing the vehicle in detail I'm intrigued, it seems wrong to me unless for
the ultimately huge cranking spark it has a 6V coil on a 24V system. The norm
is a 6V coil and ballast on 12V systems and 12V coils with ballast on 24V.
>If you bypass the resistor I
>think the coil would be toasted soon after that.
>
With a 6V coil on 24V certainly.
>Think about it, the
>only resistance between the +24 volts and ground would be the wire in the
>coil, and the point resistance. That means big currents will flow and
>something will get quite hot and fry.
>
Something like 3A - 4A is the norm for most 12 V coils, thus having a primary DC
resistance of 4 ohm and a ballast of the same value. Some 36W - 48W of power
continually dissipated in the coil will heat it up with the engine stopped and
the points closed.
For the same energy level a 6V coil would have a 2 ohm primary and with 24V
applied the resulting 12A flow would dissipate 288W, certainly enough to cook it
quite rapidly. The ballast resistor though would need to be 3 ohm with a 108W
capability; a very large device indeed.
Richard
(Southampton UK)
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