Ballast Resistor

Tech Question


Erik Bakko, Brooklyn, NY, 72 Dodge Swinger 318ci

Dear Mr. Mopar Guru,

My ballast resistors have an expected life span of 3 months in my Dart. Iput 4000 miles on the clock in the last year. I’m not sure what this littlegem does exactly, I just know that it protects other ignition circuits andI’m shot down without it.

Standard Ignition Products rate theirs as “universal”. I’ve burned outtwo of those.

Mopar Performance has three different models (0.25, 1.0 and 1.4 ohm)Haven’t tried these.

I just found my new Mallory cracked in the middle yesterday. Super glue,zip ties and positive thinking are keeping me up and running. This wassupposed to be rated for 0.75 – 1.5 ohms and offer variable resistance.Seemed substantial enough but it may have cracked last weekend when I drovein a downpour on the highway for 5 hours. I’ll ask about phantom dash leaksanother time.

The car has a fresh’nd 318 with a new Mopar orange ignition box, 50 ampalternator, stock distributor, new Mopar voltage regulator, MSD Blaster 2coil, new Moroso wires and Accel plugs. Other than that, nothing much isdifferent than stock with the ignition. It starts and runs beautifully.

Please offer any thoughts you may have and what I might do to avoid havingto waste my time thinking about this little piece of pottery. I just wantto know what it does and get one (and a spare) that works.


Erik, first, I need to know what the battery voltage is at 2,000 – 2,500RPM. If it is much over, say, 14.2 – 14.5 volts, that’s part of the equationOffhand, the Blaster 2 coil, which, I belive, is designed for C-D or MSDignitions systems, probably draws too much current when used in a simpleswitch-type electronic ignition (such as yours). Swapping to a stock coiland stock ballast would be the easy fix.

Otherwise, you’re probably exceeding the 20 or 25 watts dissipation mostballast resistors are likely rated at. The only fix at that point would betwo fairly high resistance ones (>1.25O ) paralleled or 2 low- resistanceones (approx 0.5O) in series — either would do the trick. But, with theBlaster coil, the “Orange Box” is almost certainly handling more currentthan it is designed for and is next in line to take a bullet.

There’s only one other thing I can think of: Possibly you have some wiringerror so that the ignition-run circuit (the ballasted one) is also feedingsomething else; therefore, too much current would be flowing through theballlast. The test: disconnect the ballast and be sure no other circuitshave stopped working.


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