Ballist Resistor

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I have a 68 Plymouth fury iii 318 2bbl it has what looks like ballist resistor behind the dizzy with two wires one to ground and other wire to looks like another resistor with 3wires on it on drivers fender well any help would be great I like to put Petronix in it how do I know what to bypass etc.

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That ballast resistor behind the distributor is for your wiper motor. Don't screw with it, they are expensive and hard to find the correct one. That gives you the slower wiper speed.

Your ignition ballast resistor is over by the hood hinge on the driver side.
 
I have a 68 Plymouth fury iii 318 2bbl it has what looks like ballist resistor behind the dizzy with two wires one to ground and other wire to looks like another resistor with 3wires on it on drivers fender well any help would be great I like to put Petronix in it how do I know what to bypass etc.

View attachment 557910

View attachment 557911
If you want another option from the petronix, although totally sacrilegious, I'm playing with converting mine to HEI ignition with an e-core coil. I'm having a couple aluminum mounting brackets made for everything and can send pics hopefully after this weekend. I know there's the guy who makes a bracket that mounts the module under the factory magnetic pickup but I wanted to keep it away from the engine heat and also not just throw it on the firewall or something. In actuality you won't even know it has HEI by looking at it other than the E-core coil drawing questions because I gutted an old mopar electronic ignition module and wired it through the oe terminals that go thru that harness. Even soldered a jumper wire in the ballast resistor and removed the resistor portion from the back of the ceramic portion. I will have to run it here in the AZ heat to make sure the module cools properly the way I made it. I know some will ask why but my answer is always just to see if I could and to keep people guessing at things when I pop the hood.
 
The ballast resistor is/was critical to point life, takes current down from 12V to around 6V for a smaller spark (and to keep from burning the coil when ignition is left on with points closed, the coil gets HOT!) mitigated by the condenser which is usually junk, over or under spec, one condition causes burning on one side of the points, the other condition the other point face, with resulting pitting on the other side.

It limits current, not voltage some would say, and has differing rates of resistance based upon heat, cold readings of either voltage across or DC resistance are not the whole story.

The dual ballast resistor circuit gives higher voltage rate to the ignition (8-10V) while cranking (bottom side of the 4 prong resistor) then reverts to the lower voltage for cool running.

I'm not a fan of electronic distributors, fried modules make for very unpleasant situations. From the miserable early days of electronic ignition, it's a wonder Chrysler didn't go bankrupt, cars stalling at lights when warm because of goofy pickup coils going gunnybag when hot.

Later, Mallory Unilite modules were a pain in my rear with balanced blueprinted 383HP in Satellite Sebring Plus.

I prefer to install NOS Mallory K118 points and condenser, will probably never need to be changed again in my lifetime.

The next step is a Mallory dual point, which you can run as a single point no problem, and you get a tight shaft/bushing on needle bearings, plus any advance curve you want, being able to control total advance. And you get rid of the vacuum advance forever, and potential air leak/failure.

If you open your points (from closed) at night w/ key on, you should see a teeny weak red/orange spark. If it's big fat and blue, your points won't last, obviously an under capacity of the condenser to control the spark.
 
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I have a 68 Plymouth fury iii 318 2bbl it has what looks like ballist resistor behind the dizzy with two wires one to ground and other wire to looks like another resistor with 3wires on it on drivers fender well any help would be great I like to put Petronix in it how do I know what to bypass etc.

View attachment 557910

View attachment 557911
The resistor on the drivers side is for the ignition and the one on the center of the firewall is for the wiper motor.
 
The ballast resistor is/was critical to point life, takes current down from 12V to around 6V for a smaller spark (and to keep from burning the coil when ignition is left on with points closed, the coil gets HOT!) mitigated by the condenser which is usually junk, over or under spec, one condition causes burning on one side of the points, the other condition the other point face, with resulting pitting on the other side.

It limits current, not voltage some would say, and has differing rates of resistance based upon heat, cold readings of either voltage across or DC resistance are not the whole story.

The dual ballast resistor that has a higher voltage rate to the ignition (8-10V) while cranking (bottom side of the 4 prong resistor) then reverts to the lower voltage for cool running.

I'm not a fan of electronic distributors, fried modules make for very unpleasant situations. From the miserable early days of electronic ignition, it's a wonder Chrysler didn't go bankrupt, cars stalling at lights when warm because of goofy pickup coils going gunnybag when hot.

Later, Mallory Unilite modules were a pain in my rear with balanced blueprinted 383HP in Satellite Sebring Plus.

I prefer to install NOS Mallory K118 points and condenser, will probably never need to be changed again in my lifetime.

The next step is a Mallory dual point, which you can run as a single point no problem, and you get a tight shaft/bushing on needle bearings, plus any advance curve you want, being able to control total advance. And you get rid of the vacuum advance forever, and potential air leak/failure.

If you open your points (from closed) at night w/ key on, you should see a teeny weak red/orange spark. If it's big fat and blue, your points won't last, obviously an under capacity of the condenser to control the spark.
Current is measured in amps not volts, two different things. Think of the voltage as the driving force behind electricity and current(amps) as what's being driven. A resistor in an electrical circuit can and usually will change both current and voltage if you look at how ohms law works. Some of your terminology and thought process with electronics is a little off.
 
Current is measured in amps not volts, two different things. Think of the voltage as the driving force behind electricity and current(amps) as what's being driven. A resistor in an electrical circuit can and usually will change both current and voltage if you look at how ohms law works. Some of your terminology and thought process with electronics is a little off.
I have one of these t shirts. QED…

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Read online;

"The ballast is a series resistor which limits the current in the coil. The ballast resistor also drops some of the voltage but voltage reduction is not its primary function."
 
If you want another option from the petronix, although totally sacrilegious, I'm playing with converting mine to HEI ignition with an e-core coil. I'm having a couple aluminum mounting brackets made for everything and can send pics hopefully after this weekend. I know there's the guy who makes a bracket that mounts the module under the factory magnetic pickup but I wanted to keep it away from the engine heat and also not just throw it on the firewall or something. In actuality you won't even know it has HEI by looking at it other than the E-core coil drawing questions because I gutted an old mopar electronic ignition module and wired it through the oe terminals that go thru that harness. Even soldered a jumper wire in the ballast resistor and removed the resistor portion from the back of the ceramic portion. I will have to run it here in the AZ heat to make sure the module cools properly the way I made it. I know some will ask why but my answer is always just to see if I could and to keep people guessing at things when I pop the hood.
I already did that on my 73 back in 2019.
 
That ballast resistor behind the distributor is for your wiper motor. Don't screw with it, they are expensive and hard to find the correct one. That gives you the slower wiper speed.

Your ignition ballast resistor is over by the hood hinge on the driver side.
Hi Big John, I have a 68' 300 and do not see any ballast for the wiper in the service manual. I have a three speed motor installed and all seems to work. Is this resistor only on certain cars? Thanks.
 
Hi Big John, I have a 68' 300 and do not see any ballast for the wiper in the service manual. I have a three speed motor installed and all seems to work. Is this resistor only on certain cars? Thanks.
You'll see that resistor on 2 speed wiper motors.

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