Re: IML: Ballast resistor

["Bill Watson" <wwatson5@xxxxxxxxx>]

Actually, the original purpose of the ballast resistor was to protect the
points.   Running 12 volts into the ignition system was found to wear out
the points fairly qucikly, so when auto manufacturers switched from 6 to 12
volts they introduced a resistor.   As the coil boosts the power to the
ignition system, the ballast was placed before the coil.  Result, the coil
was actually a 6 volt unit and a number of makes continued to use the same 6
volt coil on the 12 volt system.   The resistor does protect the coil as
well, but only because it is basically 6 volt coil that had to be used as it
was placed after the resistor.

>From the 1963 Plymouth-Valiant Service Manual :
"The ballast resistor is a fixed resistance in the ignition primary circuit.
During low speed operation, when the primary circuit current flow is high,
the ballast resistor temperature rises, increasing the resistance.  This
reduces the current flow, thereby protecting ignition point life.  At high
speed operation, when the primary current flow is low, the ballast
resistance cools off allowing more current flow, which is required for high
speed operation .  During starter operation, the ballast resistor is
bypassed, allowing full battery voltage to the ignition primary cicuit."

And which is why many electronic systems can use a 12-volt coil and no
resistor - no points to burn out.

And I believe this rising and falling in ballast resistor temperature does
have some effect on the life of the resistor, especially as it is surrounded
by procelain.  The ballast resistor on a 1965 Valiant I owned died and had
to be replaced.  When I pulled the old one off the cowl, one end of the
resistor wire inside fell out - it had broken about half an inch from the
end.

Bill
Vancouver, BC



----- Original Message ----- 
From: "Rob P" <fristpenny@xxxxxxxxxxx>
To: <mailing-list@xxxxxxxxxxxxxxxx>
Sent: Wednesday, June 15, 2005 7:10 AM
Subject: Re: IML: Ballast resistor


> The ballast resistor is to protect the coil.  Some aftermarket coils don't
> require a resistor.  This is probably the case with your MSD system.
>
> >From: "Klebert L. Hall" <swampyankee@xxxxxxx>
> >Reply-To: mailing-list@xxxxxxxxxxxxxxxx
> >To: <mailing-list@xxxxxxxxxxxxxxxx>
> >Subject: Re: IML: Ballast resistor
> >Date: Tue, 14 Jun 2005 22:25:04 -0400
> >
> > >Subject: RE: IML: Ballast Resistor
> > >
> > >Dick the ballast master and fellow IMPers,
> > >Whet to start the 63 after 3 years of sitting. Found 3 bad lifters
before
> > >and replaced the lifters and push rods. I replaced the points with the
> > >electronic (the under the cap version). Car started right up and I was
> > >breaking the the lifters and the car sputters, dies , and no start. I
had
> >a
> > >buddy turn it over and had good spark. BUT, I look over and see the
> >ballast
> > >SMOKING!
> > >Looked around again and the newly rebuilt carb had a lake of gas on
each
> > >side.
> > >-Charles Major
> >
> >    When my mechanics put an MSD in my '69, they took the ballast
resistor
> >out of the circuit... Maybe your system uses a different setup, though.
> >
> >      -Kle.
> >      '69 Crown 4DHT
> >
> >



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