Let's Talk 'Ballast Resistors'

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archlab

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I'm a real exciting guy...I get down on real compellin' topics like Broads, Booze & Ballast Resistors.

Anyway, Here's my main question:
Is there a benefit of switching from a 4-Prong B/Res, to a 2-Prong (or vice versa)?
I ask because I've got 2 small block vehicles, both w/ the Orange Box ECU (retro-fits). One is a 1969 D-100 Pickup & the other is a 1968 Dart.
The Electronic Ignitions are pretty much identical, but the Dart (for some reason, I can't remember why) has a 4-Prong B/Res, the D-100 has a 2-Prong B/Res.

The D-100 always seems to start & run smoother. Now, I know that I haven't given a load of info, plus there are differences in the two vehicles that may have implications outside the scope of the mightey Ballast Resistor, but if all things were equal, would the difference in B/Res' make a difference in performance?

Thanks.
 
The difference isn't in howm any posts they have. Most modern ignition systems and modules use only 2 of the contacts anyway.
The factor that makes a difference is the resistance between the 2 contacts.
A 4 post resistor is actually 2 resistors with 2 different values built together in one part.
So if your ignition was using the wrong 2 contacts the performance would change.
 
For an Elec-novice like me, cutting out that extra 'point of failure' seems appealing.
I've got the 4-Pronged B/Res wired right, so I'm probably able to rule out the B/Res as the culprit. I'm kinda thinking my issue is.....the Bulkhead Connector (namely, ythe middle one).

Anyway, I'm glad to get some feedback on the B/res though, because I've always kinda known what they do, but never really got into their true purpose & effects.

One other question: If one did have the 4-Prong B/Res wired wrong, Would it cause any damage to the B/res...or other components down the line?
 
The reason you would need a 4 prong resistor is IF you have an older "5 pin" ECU, and now you definately do not want to switch it around. If you look at this diagram, and a resistor, one end of the resistor has a U shaped cutout, which originall fit a "key" in the connector. That's how you ID the right end of the resistor

You cannot tell a 4 or 5 pin box by looking ALL of the time. Some 4 pin boxes have 4, some have 5 pins. So if you suspect a box with 5 physical pins is really a 4 pin box, you must use a meter on the 5th pin to discover if it's hooked to anything, or a dummy

Also, if you have the system correctly wired with a 4 pin resistor for a 5 pin ECU, you can use EITHER a 4 or 5 pin ECU

5 pin ECU, 4 pin resistor: "U" cutout on the bottom of the resistor

Ignition_System_5pin.jpg


4 pin ECU, 2 pin resistor:

Ignition_System_4pin.jpg
 
Thanks! It looks like I'm wired right. It's been a few years, so my specifics are a bit fuzzy, but here's what I recall about the Dart - the ECU & Distributor kit from Mopar Perf was new (so we can rule out the older ECU possibility), but I think that the 4-Pronged B/Res was already in-place & wired up. I dunno why I didn't go w/ a 2-Pronged setup - maybe the exist wiring leant itself better, or maybe I just figured that the car was supposed to have a 4-Prong B/Res (that's what half-info will get - confusion).

But from your post, it seems that the ECU is OK w/ this setup, so It's looking like I'll need to search other areas in the Elec/ Ignition System for performance / drivability improvements.
 
273 explained it thoroughly (as usual). You might want to search for posts on an HEI ignition module, since lets you get rid of the ballast and use a hotter coil. It would only be a marginal improvement to your Mopar ignition though.
 
I've definitely gotten interested in all the posts about the HEI. I've already done the MP ECU upgrades on my vehicles (except for the '60 NY'r) already & am pretty happy w/ them. The promise of the HEI has peaked my interest. But if 'marginal improvement' is the result, then I may just wait until I take on a new project, so that I don't need to redo work already done.

Anyway, another 'thanks' to the knowledgable.
 
I have a question on this as well. On my 68 it has 2 posts but there are 2 wires going to each post. I see that one is to reduce voltage to the points but what is the other? I was going to use a hei style dist with separate coil and was redoing some of the wiring harness so thought I would just eliminate the ballast resistor. All it's wires and the connections are good so should I just bridge it instead?
 
Hersbird said:
I have a question on this as well. On my 68 it has 2 posts but there are 2 wires going to each post. I see that one is to reduce voltage to the points but what is the other?
Click to expand...


One is to reduce the voltage to the coil (through the points or reluctor pick-up) and the other is for the 5 pin ECU's use...

If you have the dual ballast set-up you can use either the 5 pin ECU OR the 4 pin ECU. If you have the single ballast you MUST use the 4 pin ECU only.

The 5 pin ECU required the second resistor for its internal circuitry which was not required for the 4 pin ECU
 
additional;

I myself like to use the dual ballast wiring when converting from points to electronic so that I dont have to worry about what ECU to stick in there... 4 or 5 pin works in both setups
 
Hersbird said:
I have a question on this as well. On my 68 it has 2 posts but there are 2 wires going to each post. I see that one is to reduce voltage to the points but what is the other? I was going to use a hei style dist with separate coil and was redoing some of the wiring harness so thought I would just eliminate the ballast resistor. All it's wires and the connections are good so should I just bridge it instead?
Click to expand...

That would be the original setup which is fine. Here's how it works... One wire goes to the coil. The other wire there with it is brown and hot in start to send all 12 volts to the coil. Same as if the connector was pulled of the ballast . At this point the connector may as well not be there.
When the switch return to the run position the power comes to the balleast on the dark blue wire. Only way that power can get to that wire that goes to the coil is through the ballast resistor. So... all connectors good, switch in run, there will be reduced voltage going to the coil and back up that brown wire to the ignition switch ( which doesn't matter ).
I hope this makes sense.
 
Hersbird said:
I have a question on this as well. On my 68 it has 2 posts but there are 2 wires going to each post. I see that one is to reduce voltage to the points but what is the other? I was going to use a hei style dist with separate coil and was redoing some of the wiring harness so thought I would just eliminate the ballast resistor. All it's wires and the connections are good so should I just bridge it instead?
Click to expand...

RedFish said:
That would be the original setup which is fine. Here's how it works... One wire goes to the coil. The other wire there with it is brown and hot in start to send all 12 volts to the coil. Same as if the connector was pulled of the ballast . At this point the connector may as well not be there.
When the switch return to the run position the power comes to the balleast on the dark blue wire. Only way that power can get to that wire that goes to the coil is through the ballast resistor. So... all connectors good, switch in run, there will be reduced voltage going to the coil and back up that brown wire to the ignition switch ( which doesn't matter ).
I hope this makes sense.
Click to expand...

wrjjol.jpg


Except Red left out the 4th wire.

1 One side is power coming out of the bulkhead from the IGN switch TO the resistor, and the branch wire feeds the regulator "I" terminal

2 Coil side, as Redfish says, is goes to coil, brown is the bypass circuit

Mopar is the only brand that wires the bypass this way. Ford, IHC, AMC, GM, all used a separate contact on the starter solenoid.
 
I can tell you this. After installing my aftermarket ignition system it was thrill to toss that ballast in the trash and not worry about it. Not mention I have a rev limiter now... lol
 
mullinax95 said:
I can tell you this. After installing my aftermarket ignition system it was thrill to toss that ballast in the trash and not worry about it. Not mention I have a rev limiter now... lol
Click to expand...

I don't get all the hand wringing over resistors. MILLIONS of cars drove MILLIONS of miles all over the world using ballast resistors

In the US, GM and Ford put them "in" the harness as a length of resistive wire

I don't think I've replaced 5 of em since I started driving in 1965
 
on the diagram I have it looks like the dk blue w/tracer goes to the ignition and the brown goes to the wiper switch?
Oh wait, wrong brown! I see it now. So In start it sends 12v down the brown but in run that lead is basically a deadhead off the regulator and the regulator give less then 12 to the coil on that. The blue to blue with tracer is basicaly a splice and always 12 to signal the voltage regulator. I think the simpliest way is to just bridge the regualtor and leave it in.
Then if anybody wants to go back to points after the EMT blast it will be easy!
 
I dont understand why so many want to get rid of it either.
The ballast resistors purpose is to protect the coil from over heating. If it should fail you can put the wires together and run without it until you reach one of the many part stores
 
What kind of voltage should one be reading at the coil I'm have a minor issue since I just reinstalled my motor with 12v on the battery and 12v at the BR I'm getting around 3v to the coil and the motor just rolls over and over with no spark. But if I let the battery charge for a couple minutes I get 13v at the BR and 5v at the coil and the motor will run very good
I'm confessed because I didn't have this problem before if the motor would roll over it would start no problem now I checked all the wiring and every thing is hooked up right with nothing damaged
I'm running pertronix ignitor with a blaster coil on a Turbocharged SLANT 6
 
12 volts to the coil in start and around 7.5 in run.
 
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