Distributor Wiring Diagrams

[D Cluley]

I was looking at options for replacing a distributor and made up these diagrams to help sort out what was needed. Thought it might be useful to have them all together in one place. Let me know if you have any questions/corrections.

1. Original points style distributor.

2. Points distributor with Pertronix module. Pertronix shows 2 different ways to wire their module depending on whether or not you are keeping the ballast resistor and I did mine a 3rd way. I don't remember where I got the info to do it my way, but it seems easier and has been working for 15 years or so. Your mileage may vary.

2a. From the Pertronix instructions with a ballast resistor.

2b. From the Pertronix Instructions without a ballast resistor. You need to check the coil for proper resistance to eliminate the factory ballast resistor.

2c. My Way

3. Original 1970s style Electronic Ignition with 5 pin box and 4 prong ballast resistor.

4. Newer Electronic Ignition with 4 pin box and 2 prong resistor.

 

[Big_John]

You don't want to power the Pertronix Ignitor after the ballast resistor as shown in your drawing. Actually, you don't need to use the ballast resistor with the Ignitor as long as your coil has primary resistance between 1.5 and 3.5 ohms and with the Ignitor II, their instructions are not to use it. Ignitor III also doesn't use the BR and also uses a lower primary resistance coil than stock, but that's another story.

Ignitor II:
https://cdn.shopify.com/s/files/1/0247/6913/4628/files/91385LS.pdf

Ignitor:
https://cdn.shopify.com/s/files/1/0...000-008707_1361A_1381A__rev2.pdf?v=1741975748

 

[D Cluley]

I wondered about that. I saw a diagram with the ignitor bypassing the resistor. On the other hand, my ignitor I that has been wired straight to the coil like my drawing for 15 years without any problems so I'm not sure what to think.

My recollection is that maybe with the ignitor 2 or 3 having straight 12v is more critical?

 

[Polara_500_Jr]

I removed the ballast when I put the ignitor3 in a while back. I did install their branded coil with it as well.

 

[D Cluley]

I have updated this with the 2 versions that Pertronix recomends.

 

[Big_John]

I have updated this with the 2 versions that Pertronix recomends.

2a is not the way that Pertronix says to wire with a ballast resistor.

Chrysler has "start" and "run" circuits. The Pertronix wiring diagram for use with the BR does not show those circuits. Basically it's 12 volts to the Pertronix unit with the BR to the coil.

The way you show it wired, the Pertronix is wired through the BR on "start" which means it will have limited current during "start" and full current on "run". So you have less voltage to the Pertronix when you are starting the engine.

If you really want to run the BR for the coil, then you have to run a dedicated 12 volt circuit to the Pertronix that won't limit current with key position.

This is how this Pertronix wiring diagram is laid out.

Regarding the way you've wired your car, I don't understand why you want to compromise a good ignition system with not powering it correctly. Why not optimize the system? Pertronix is pretty clear about powering the unit with a 12 volt source. If you don't have enough primary resistance in your coil, I can understand using the BR in the wiring to the coil (just the coil) but that's an easy fix with the correct coil.

It is a good testament to the Pertronix being able to run at a wide voltage range though, even if not optimally. I really encourage you to do the math for this so you can see the voltage drop yourself though.

Myself, I run a Pertronix II in my '65 Barracuda. I use their .6 ohm primary resistance coil with no ballast resistor. The Pertronix II is a better system and if nothing else, won't fail like the standard Pertronix will if the key gets left on.

 

[D Cluley]

John, thank you for taking the time to work through this with me. As you can see, I almost know what I'm doing here.

As to 2a, I could see the problem with the start position dropping the voltage but couldn't see a way around it. I am wondering if that Pertronix diagram is generic and really only applies to something wired differently than our Mopars. I can't see a way to get straight 12 v in both start and run without that connection backfeeding full voltage to the output side of the ballast resistor. Maybe something with a relay? but that is getting way too complicated to solve a problem that probably doesn't need to exist.

As to why I wired it the way I did, the short answer is "it seemed like a good idea at the time". I am sure it was suggested someplace as I didn't know enough to come up with it on my own. I think part of it was the desire to easily go back to points if the Pertonix failed. (It's been at least 15 years, so that probably was overthinking) and part was conflicting info about Pertronix with the stock coil and whether that needed the resistor. I actually still have questions, but not enough functioning brain cells right now to ask, will probably start another thread this weekend. Today turned into one of those days where everything I touched got worse.

 

[Big_John]

As to 2a, I could see the problem with the start position dropping the voltage but couldn't see a way around it. I am wondering if that Pertronix diagram is generic and really only applies to something wired differently than our Mopars. I can't see a way to get straight 12 v in both start and run without that connection backfeeding full voltage to the output side of the ballast resistor.

I agree that the Pertronix diagram is generic. They sell enough Mopar conversions that they should do something more, but that's probably never going to happen.

The wiring is fairly simple though. Here's how it's wired without a ballast resistor.

If you want to run a ballast resistor to the coil, this is how you can do it.

Both diagrams are basically connecting "run" and "start" so the Pertronix is powered with 12 volts from the ignition switch while starting and running the car. With the basic Pertronix, using a coil with a primary resistance of 1.5-3.0 ohms would eliminate the need for one. Look at the primary coil resistance listed in the FSM if you still have a stock coil. It's usually around 1.5 ohms.

If your coil is less than 1.5 ohms, adding a ballast resistor brings up the primary resistance. Let's say you had a 1.0 ohm coil. The stock BR has a resistance of .5-.6 ohms. You just add the two together. 1.0 + .5 = 1.5 ohms.

With the Pertronix II, the coil just needs to have greater than .45 ohms primary resistance. These are values taken directly from the Pertronix instruction sheets. IMHO, the Pertronix II is the better unit and is the one to buy. You can use your stock coil with this or better yet, replace it with a lower resistance coil.

If you wanted to use a relay, you could wire it like this. I don't think it's needed, but here ya go. 12 volts could be sourced a lot of places and does not have to be switched. If I were to do this, I would probably use the battery connection at the starter relay.

FWIW, on my Barracuda, I left the BR on the firewall, but gutted the resistor and soldered a piece of wire across it. That was purely for stock appearance and a convenient way to connect "run" and "start".

 

[Big_John]

And since I touched on the subject of coils, here's a quote from Don Lindfors from PerTronix via a Hot Rod mag tech article.

"The Flame Thrower 40,000V coils have internal resistance rated at 1.5 or 3.0 ohms. The 3.0-ohm coil should be used on PerTronix Ignitors installed on four- and six-cylinder engines while 1.5-ohm coils should be used for eight-cylinder applications. These coils can be used on virtually any inductive (non-capacitive discharge) ignition system.

Flame Thrower II coils have lower resistance, 0.6 ohms for use with Ignitor II ignition systems as well as many other high-energy ignitions. The low resistance helps to produce up to 45,000 V. This higher voltage allows larger spark plug gaps for added power and better fuel economy.

Flame-Thrower III coils were developed for use with the new Ignitor III electronics. The extremely low resistance of 0.32 ohms results in 45,000 V and a coil that charges to peak, current typically 30-70 percent faster the other coils. It should be noted that these coils are compatible with Ignitor III electronics only."

 

[D Cluley]

Ok, so your version of 2a provides full voltage to the Pertronix unit even during "start" but does not bypass the resistor to give the coil extra voltage during "start". Clearly Pertronix just wants you to eliminate the resistor. (Yes, I am aware that you said that several days ago. ) It has just taken a while for me to work through all of this and I did start another thread where I laid out what I think I know. Musing on Ignition systems

The other part is that this all comes from starting a project last weekend that I should have left alone because I have multiple out of town cruises & tours planned for the next couple of weeks. My current thought is to keep it the way that has been working for years and then look into eliminating the ballast resistor later this fall.