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what keeps killing ignition boxes

magvan

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In 2 of my mopars i keep going through ignition boxes.
in my coronet they work for awhile and then all of a sudden they seem to randomly get hot and turn off. let them cool off and drive it home usually with them dieing a couple more times on the way. i think im on the 3rd or 4th box this car has also killed about 5 ballast resistors, 1 distributor pick up, and a pertronix. i have just recently switched to an HEI module on this car, so ill see what happens

my pick up has been fine for about a year and a half but now last week the truck was running wednesday when i parked it and on saturday, no spark the box is completely dead. replaced the box and it fired right up and has been fine until this morning, i get a block from my house and died, walked home got another box and tools, changed out the box and fires right up. think this is the 4th box on the truck now. when i bought it the box was dead

i have used military surplus boxes, mopar orange box, standard chrome box, even tried no name box. all of them were/are made in the USA boxes
 
Something is wrong with the wiring to burn them out, maybe at the ballast resistor
 
Shorted turns in the coil or coil with too low of impedance allowing too high of currents in the switch device in the ignition box
 
I never have burnt a ballast resistor in all my life! I'm really amazed about how the ppl talks about this fail as a common fail!

( I hope my car doesn't hear me )

I woud check the alt output at iddle althought my car was an ECU eater too sometime in the past and I know my Charging system is quite perfect.
 
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I had a bad OEM (mechanical) regulator that was overcharging. I was told the the ECU's do not like that. Sure enough, not long after I replaced the regulator with a Wells VR706 regulator the ECU died and left me on the side of the road. Replaced the ECU and she fired right up.
 
In my experience a little water will kill a hot ballast right now. I think Jim is onto something, so Jim what impedance shud a coil be for say OEM style electronic? I don't think my instructions ever said & would pertronix, others be different?
 
In my experience a little water will kill a hot ballast right now. I think Jim is onto something, so Jim what impedance shud a coil be for say OEM style electronic? I don't think my instructions ever said & would pertronix, others be different?
I don't know. I have my OEM coil off my 318 that is on the bench to take it to work and measure.
 
All my ECUs killed were with a MSD blaster 2 coil. All Mopar Performance aaaaand the FBO A688
 
All my ECUs killed were with a MSD blaster 2 coil. All Mopar Performance aaaaand the FBO A688

Yup, coils really need to be matched to the box that drives them...... you can never tell if you are over stressing the switch.
 
So ypu say, a MSD blaster 2 is unmatched to the Mopar Performance ECUs?

I remember even Don from FBO sells its own coil, he tolsmme a blaster 2 is a good option for its ECU ( the one from back in the days )
 
So ypu say, a MSD blaster 2 is unmatched to the Mopar Performance ECUs?

I remember even Don from FBO sells its own coil, he tolsmme a blaster 2 is a good option for its ECU ( the one from back in the days )


Now it is do NOT use a Blaster with his FBO.

"DO NOT use any Blaster, Accell or parts store Coil, they are incorrect for the Micro-Processor Type FBO Ignition Box."

 
Galley. Its been there for years and no problem yet. Same original /6 ecu from the mid 70s and blasster coil. Have not lost an ecu grounded properly yet. Lost plenty before fixing the ground issue.
 
In 2 of my mopars i keep going through ignition boxes.
in my coronet they work for awhile and then all of a sudden they seem to randomly get hot and turn off. let them cool off and drive it home usually with them dieing a couple more times on the way. i think im on the 3rd or 4th box this car has also killed about 5 ballast resistors, 1 distributor pick up, and a pertronix. i have just recently switched to an HEI module on this car, so ill see what happens

my pick up has been fine for about a year and a half but now last week the truck was running wednesday when i parked it and on saturday, no spark the box is completely dead. replaced the box and it fired right up and has been fine until this morning, i get a block from my house and died, walked home got another box and tools, changed out the box and fires right up. think this is the 4th box on the truck now. when i bought it the box was dead

i have used military surplus boxes, mopar orange box, standard chrome box, even tried no name box. all of them were/are made in the USA boxes
I'm sure there are other reasons for this issue but here is my spin on it. When I converted my 65 Sport Fury to electronic ignition, I had the same issue. the orange box got hot and would open up the circuit shutting down the engine sometimes after 15 minutes of driving. The coil was hot and I blamed that at first and replaced it to no avail. I finally found that my ignition box was not grounded properly and that was causing all of my woes. My digital ohm meter showed about 18 ohms between the box and neg on the battery. I scraped some paint off of the mounting area and got the resistance down to .2 ohms. That same orange box has been on that car for the past 15 years with no issues. My recommendation to anyone with this issue is to check the resistance between the box and neg on the battery. Anything more than .5 ohms is too much in my opinion.
 
To really go back in time my old dist. went south last summer; Accel BEI that control box had a dedicated ground & ran one of those gigantic Accel supercoils for many many yrs. when it died I just went with Summit's changeover electronic and a stock autozone coil, now I'm worried the coil might be wrong.
 
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image.jpg
 
To really go back in time my old dist. went south last summer; Accel BEI that control box had a dedicated ground & ran one of those gigantic Accel supercoils for many many yrs. when it died I just went with Summit's changeover electronic and a stock autozone coil, now I'm worried the coil might be wrong.

If you have an oscilloscope you can easily check and see how things are working :) . I mentioned this once to someone a while ago while working on their FiTech FI system not expecting much but they came back with scope shots from a scope he borrowed from a relative!

Also depending on the sophistication of the box it may have current limiting like modern cars and in that case there it likely no issues with the coil. All you need to be sure of is the current in the primary is not going high enough to damage the switch. If the box is not getting hot then I would guess it is fine on that front. The bad ground is a good one. I have been trying to decide how that could kill the switch. At first glance you would think that the 20 ohms would have limited the current to an easily safe place. What may have been happening is the ring back clamp that protects the switch from over voltage on the spike that occur when the spark fires and the switch opens may have dependent on that ground as well. It may have been over voltage and secondary break down failures on the switch in that case.
 
Go back to basic electronics. A bad ground requires more amps to power a circuit. Voltage should drop instead of spike. With drop in voltage and increased amp = excessive heat and melt down.
 
Go back to basic electronics. A bad ground requires more amps to power a circuit. Voltage should drop instead of spike. With drop in voltage and increased amp = excessive heat and melt down.

That is for a constant power load. This is not it is a voltage source clamped across an inductor (coil). V=L*dI/dt. Where V, L and dt (at a given RPM) are constant. So the peak I is equal to V/L*dt. The resistance will drop some of the 12V across it so the peak I in the inductor will be smaller because the L does not see as much V across it.

Put the resistor in the circuit here and do the math. Peak Current is smaller.

https://www.ratwell.com/mirror/users.mrbean.net.au/~rover/ketterin.htm
 
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