BALLAST RESISTOR

[stevekarlo]

What is the difference between a single and double ballast resistor?

I had a single on my 73 with electronic ignition and an excell coil and an aftermarket MP distributor (Can't remember if The single plug resistor came with the coil or new distributor, but the car originlly had a  double resistor with the original ignition ) Its been on there for years and I have forgotten why the single is on the car, but this morning it gave out. I had a double one to replace it with. It did the job but I am getting getting crazy backfiring. Not sure if the backfiring is from the electronics or bad gas/fouled plug/ bad plug wire. The backfiring occurs under load but at idle it sounds like I am missing a cylinder or two.

[Nacho-RT74]

dual ballast feeds an extra positive on the 5 pins modules, which changes the voltage ( for whatever reason ) with engine bay temp variation and RPMs.

single ballast resistor works with 4 pin modules. These modules setup changed the variable secondar resistor to inside the module so thats the reason why this extra or secondary resistor built on dual ballast is not needed.

The pin gone on module is the one what gets the power from the secondary resistence from dual ballast.

you can fit a 4 pins module on a stock 5 pins module setup, simply the secondary resistance wiring will get to nowhere ( the empty pin location through the green traced red wire ), however a 5 pins module will work incorrectly on a setup changed to single ballast resistor

[stevekarlo]

I do have the chrome box on the car. Have to look but I think that is the  pin set up.

[Nacho-RT74]

chrome Mopar box is 4 pins and can use anyone of them, although single HP is recomended ( around 0.8 ohms ). However Mopar advertises to sell a 1/4 of ohm piece for HP purpouse