Electronic ignition, two wire or four wire ballast resistor

[moparhunter]

I’m converting my 69 Dart over to a stock style Dodge electronic condition.
Is there any plus / minus between the four wire balls, resistor, or the factory two wire ballast resistor ?

 

[remytherat]

Must use four pin ballast for 5 pin ecu.

Two or four pin ballast for 4 pin ecu.

 

[moparhunter]

Is there a reason to use the four or five is one better than the other?

 

[Kendog 170]

Most now are 4 pin so I would take that route.

 

[toolmanmike]

I have a 4 pin. 5 pin will just make things unnecessarily complicated.

 

[Professor Fate]

Either one will work fine.
If I'm converting, I usually wire it up with a four pin ballast. That way, I can run either a four or five pin ECU if I have a failure in the future.
As said, most all new ECUs are four pin, but I have a number of early five pin ECUs that I can use as spares should the need arise. The ability to use "whatever" to get back on the road is a bonus in my book.
If you're looking to use an aftermarket "Hi-po" ECU, they're all going to be four pin. Some don't even require the ballast, check with the manufacturer.

 

[toolmanmike]

This is all you need. This diagram is for a 4 pin and is simple to understand. The start position wire on the "out" side of the ballast is very important. The "run" position wire feeds the ballast and the ECU when you let off the key.
Also remember, the wire positions on the ECU are the pin positions and not the sockets in the connector when you unplug it and turn it over to look or test. It took me a while to get that through my thick head. Also make sure the ECU is grounded well. Use a toothed washer and clean the paint from the screw hole. I installed nutserts to provide a solid ground. The 1/4" bolts sill stay tight.

 

[67Dart273]

^^THIS. The earlier ECUs had a separate power supply wire needing a resistor, that supplied part of the circuit. I doubt anyone is selling 5 pin ECUs unless you run into a NOS and it would have to be fairly old

 

[azaustin]

Just curious why they ran a ballast resistor on an electronic ignition. Never really understood why they used it on points-type ignitions either, except perhaps to lower current flow across the points. From an electronic standpoint, it seems like you just wind your coil at a ratio that would give you the desired step-up voltage. Hotter spark for starting? But, again, why do it on an electronic ignition? I don’t know how the Mopar electronic ignitions work. Most of my electronic ignition experience is on motorcycles. Early Gold Wings used a start on 12V, run on 6V system. Okay, you auto-electric gurus. Explain this to me. If it’s something I should have learned in kindergarten, I need to know.

 

[67Dart273]

Just curious why they ran a ballast resistor on an electronic ignition. Never really understood why they used it on points-type ignitions either, except perhaps to lower current flow across the points. From an electronic standpoint, it seems like you just wind your coil at a ratio that would give you the desired step-up voltage. Hotter spark for starting? But, again, why do it on an electronic ignition? I don’t know how the Mopar electronic ignitions work. Most of my electronic ignition experience is on motorcycles. Early Gold Wings used a start on 12V, run on 6V system. Okay, you auto-electric gurus. Explain this to me. If it’s something I should have learned in kindergarten, I need to know.

Chrysler ignitions along with many other switched electronic/ breakerless, draw current with the key "in run" but with engine stopped. A ballast can help save the coil. GM HEI do not do this, by the way

Normally, having a ballast, which must be bypassed for starting, gives you a hotter starting spark. This is true of breaker points but MAY NOT be true of Chrysler ECU. This is because starting power FOR THE ECU is actually backfed from the bypass circuit through the ballast to the ECU!!! This means the ECU gets lower voltage. The coil however, does get "full battery" when cranking.

The GM HEI has a sort of dwell /current control, if you will a built in ballast function of the electronics. Ballasts are called that because -- they are. -- They are not just a resistor. When the current through the system goes up due to RPM, the ballast heats up from the increased current and the resistance ALSO goes up which tends to DECREASE the current through it. So the ballast acts like a sort of regulator. BEAR IN MIND that the Chrysler system came into production in 71-72 or so as an option. This is pretty early in the solid state world, for high power, high temperature "stuff"

It was not long before that period that we didn't HAVE silicon transistors for high power---only germanium, and THEY were REALLY lame. Far less power handling, and more unreliable

 

[toolmanmike]

Just curious why they ran a ballast resistor on an electronic ignition. Never really understood why they used it on points-type ignitions either, except perhaps to lower current flow across the points. From an electronic standpoint, it seems like you just wind your coil at a ratio that would give you the desired step-up voltage. Hotter spark for starting? But, again, why do it on an electronic ignition? I don’t know how the Mopar electronic ignitions work. Most of my electronic ignition experience is on motorcycles. Early Gold Wings used a start on 12V, run on 6V system. Okay, you auto-electric gurus. Explain this to me. If it’s something I should have learned in kindergarten, I need to know.

The points ignition was originally designed for 6 volt systems. The ballast was needed to reduce that voltage. The ballast was used on the electronic ignition to reduce the voltage to the ECU. As a for instance, the GM HEI system uses 12 volts in. The Mopar system does not.

 

[azaustin]

I was aware of the early 6V switching to 12V in the early 50’s. Wondered if they had a hell of a lot of 6V coils left over, or something. The Mopar electronic is just a mystery without a schematic, but you can see the “TO” transistor case on the housing. Hall effect sensor fo trigger the spark? I’ll look it up and not bother anyone else. Thanks for the responses. Wasn’t trying to hijack the thread. Just wanted to know.

 

[azaustin]

The ballast as a kind of regulator I can understand. Some early Yamaha dirt bikes used a ballast resistor under the tank. As I recall, it was a 2-4 Ohm nichrome wire wound on a ceramic base, just like my Dart. The bikes would run without a battery (it was just there for DOT regs regarding the tail/brake light) but the extra current that the 1/2 wave rectifier (a diode) had to go somewhere, so, usually the lowest wattage instrument light would blow, followed by the tail light filament, followed by the brake light filament. If the ballast resistor broke (it got a a lot of pounding, even under the gas tank) the lights would start blowing in order, lowest wattage to highest.

 

[Mike69cuda]

The resistance of the coil is dynamic, not static like a resistor.

When the voltage and current across a resistor change, the resistance nominally stays the same.

When the voltage and current across a coil changes, the “resistance”, more properly called the impedance, can change dramatically.

I believe that the ballast resistor is there for a current limiting function, since it will remain constant over the frequency range of the ignition system operation.

As said above, the Mopar system was designed back in the earlier days of electronics. Not that it’s the best design, but that was the state of electronics back in the day. Brute force. You want to drop some voltage, add a big fat resistor (BFR). The are a lot more sophisticated methods of current limiting in modern electronics, hence no ballast resistors on some modern systems.

 

[azaustin]

CEMF.