Re: IML: 56 Ignition Problem

[Brad Weikert <a292@xxxxxxx>]

The ballast resistor is there to limit current.  The voltage drop is 
simply a side effect of the limited current that the ballast allows to 
pass through.  It's the limited current that prolongs the life of the 
points.

Any resistor will show the same voltage on both sides until a load is 
applied.  It's sort of like if you connect a garden hose with a spray 
nozzle on the end to a spigot.  You can hold the spray nozzle open and 
turn the spigot on until there is just a trickle of water coming out of 
the nozzle.  The pressure in the hose is very low.  Now turn the spigot 
off and the pressure in the hose will build up until it matches the 
pressure in the pipe supplying the spigot.  Turn the nozzle back on and 
the pressure in the hose rapidly drops again.  A similar thing is 
happening with the voltage in your ignition system except that it 
happens almost instantaneously.  A big difference in the ignition 
system is that unlike the garden hose which will briefly allow a large 
quantity of water through the nozzle, the ballast will not allow a 
large flow of current to pass through.  I'm not very good at explaining 
it and that's not the greatest analogy but I hope it makes since.

In any case I would try a different condenser.  I have had a bad 
condenser in the past and the engine would still run but not very well 
and it causes a LOT of excessive arcing across the points when they 
open which will fry them in short order.  Also the output voltage of 
the coil will be very low which is why the engine will run so roughly.  
The job of the condenser is to allow the magnetic field in the coil to 
collapse in a controlled manner.  It allows the voltage in the primary 
windings to rapidly but not instantaneously fall.  It's this collapsing 
of the voltage and hence the magnetic field which produces the high 
voltage in the secondary windings to fire the plugs.

Have a good day
Brad


On Feb 6, 2007, at 5:17 PM, Jeff Cantor wrote:

> Brad,
>
> Thanks for the suggestion although it has me puzzled.  I was under the 
> impression that when electrical systems went from 6V to 12V in the 
> mid-50s, the ignition systems were kept at around 6V to avoid having 
> to beef up the points.  If there is still supposed to be 12V across 
> open points, then you're going to have much greater arching across 
> those points as they close hence the damage that I've observed.  
> Wouldn't 6V across those open points produce less arching and 
> therefore less damage?
>
> Jeff
> '56 Sedan
> Trenton, NJ



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