If a ballast resistor goes is it an indication of a fault

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jerry6

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somewhere , or do these things go bad every year or so . The fuse type thing enclosed in the back was black . I was on the highway when it went , it was dry and hot , just wondering why it went bad .
I also have another resistor that has the back filled in so the resistor is not exposed , is this a better design that the open .backresistor ?
 
Check your charging voltage, does the battery "puke" acid out the top?

Where is it mounted, does it get any airflow? Might help to stick a washer underneath for a little more air

How about your ignition / coil? You running a "hot" coil or a stocker?

As much as I hear people badmouth ballasts, I didn't used to have all that much trouble. Just after Mopar ECUs came out factory, around 73, I converted my 70. Ya!! Way back then!! I ran that system in that car until I sold it about 78 and I don't think I replaced MAYBE one resistor. I ran an ECU system in my 340 Landcruiser and NEVER replaced a resistor built it about 77, just recently "junked" it out.

In other words, while they seem to fail sometimes they should NOT be a high failure item.

You don't routinely leave the key in "run" with the engine off?
 
No puking battery , mounted on firewall below lip just to the left of fender driver side . Stock coil and never have ignition in run without motor running .
Will mount it with a washer or spacer behind it, maybe it will help .
No idea how old the ballast resistor was , bought the car 2 years ago and only put about 5000 miles on it so far . . Will see how long new one lasts , hope longer than a year or 2
 
I had a ballast resistor in my one car for 16 years and it never went bad. If they are wired right you should not have any problems. The old 4 pole resistors did have some problems years ago.
 
Ballast resistors are just like any other part, they can go bad. I have had one go bad in 37 years of owning Mopars. The coil should not affect the ballast as it's downstream from the ballast.
 
people should not badmouth ballast resistors. I have only had one go on me and it was the factory dual ballast resistor from 1979, the mounting bolt was so seized into the firewall I had to cut it off and turn it out with a pair of vise grips
 
Hmmm, I didn't see any badmouthing of the resistor. With that said I believe they should be eliminated in any performance application, as they limit voltage to the plugs.
 
Badsport said:
Ballast resistors are just like any other part, they can go bad. I have had one go bad in 37 years of owning Mopars. The coil should not affect the ballast as it's downstream from the ballast.
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Uh, NO. The ballast regulates current to the coil. If the coil is a higher current high output coil that draws more primary current, the ballast will have more stress on it.
 
Badsport said:
Hmmm, I didn't see any badmouthing of the resistor. With that said I believe they should be eliminated in any performance application, as they limit voltage to the plugs.
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It depends on the application. You'd feel pretty silly with your "performance application", if you pulled up to the line only to have the engine quit because your bypassed ballast tore up an ignition box, the points, or the coil.

The big 'ol Mallory rectangular coil actually ADDED it's own resistor IN SERIES with the existing factory resistor. So in other words, even though it was an high output coil, it used MORE resistance.

I once witnessed one WITHOUT the Mallory resistor in a 55 Chiv turn into a smoldering heap of melted plastic after someone had left the key on.
 
I had a problem with popping resistors when I had an fbo ign. Spacing it with a 1/2" nut between it and the firewall did the trick.
 
67Dart273 said:
Uh, NO. The ballast regulates current to the coil. If the coil is a higher current high output coil that draws more primary current, the ballast will have more stress on it.
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But it can only draw what the ballast is allowing through. So what you are telling me is that a high output coil can pull more current through the ballast? I am not disagreeing with you, just doesn't make sense.

I installed a high output coil in my car and had to change the ballast to a .25 OHM ballast to allow more current through.

So if you are running MSD or whatever you should still run the ballast? All of my friends that have performance/race cars have no ballast.
 
Badsport said:
But it can only draw what the ballast is allowing through. So what you are telling me is that a high output coil can pull more current through the ballast?.
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It depends somewhat on the temperature characteristics of the ballast, but if you put more load on the thing, it will try and draw more current. Ohm's law. The coil is basically a resistor, so you have two resistors in series. If you LOWER the resistance of the load (the coil) the circuit will draw more current. The ballast will heat up and attempt to compensate, but it can only do that "so far."

Badsport said:
So if you are running MSD or whatever you should still run the ballast? .
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I was under the impression we were talking ONLY about factory stock ECU systems. If Mallory/ Accel/ MSD/ whoever recommends "no ballast" with their box, that's a completely different story.

MSD is same difference as a capacitive discharge, which means it works more like a photoflash--discharging a big charge stored in a capacitor through the coil. There is NO DC current through a coil in (so far as I know) most/ all MSD systems.

All that a Mopar ECU type system does is "replace the points." It is simply a magnetic triggered (distributor) that fires the coil in exactly the same way that the old points systems did.

GM HEI is "similar" but they've made changes there, which is ALSO why you can get away (most the time) with no ballast on an HEI

So we have to specify what we are referring to.
 
What does it mean if both ends of my resistor read roughly 12 volts (with the key in on position)? I was under the impression one end should be reading 12 and the other around 8 or so. And oh ya, the car won't start- no spark. I replaced the resistor a month ago as the old one died. It then worked for a while, but now back to not starting. I do have the Mopar electronic ignition kit installed. Thanks for the help.
 
flyinbysocal said:
What does it mean if both ends of my resistor read roughly 12 volts (with the key in on position)? I was under the impression one end should be reading 12 and the other around 8 or so. And oh ya, the car won't start- no spark. I replaced the resistor a month ago as the old one died. It then worked for a while, but now back to not starting. I do have the Mopar electronic ignition kit installed. Thanks for the help.
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Does it start to run and die as soon as you let go the ignition key ? That's what mine did , points to bad ballast resistor , not starting at all , no spark could mean bad coil or ECU .
Do you have a spare coil and ecu around ?
 
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