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Discussion Starter · #1 ·
What would cause an ignition module to keep frying? I have done the TFI ignition upgrade, with new coil,distributor cap, and wires. This is on a CJ with a freshly rebuilt 360 and a new painless wiring harness. I drove it to work for like 3 weeks and it was fine, then it starts frying modules. I check it today and find out the alternator is not charging like it should and is shot. Would this cause it to fry modules? I have gone through atleast 4 or 5. any ideas?
 

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Having a bad (shorted) diode in an alternator will fry a cheap ignition module in a heartbeat. You pay for what you get. The price difference is for the A/C waveform protection device in the module. Check or replace the alternator.

Elusive is correct about the resistor, but you should wire in a "crank by-pass" circuit. During crank, the battery voltage drops very low. If the voltage drops below 9.6 volts, the coil won't fire. Wiring a crank bypass circuit takes the ballest resistor out of the circuit during crank for this purpose.
 

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Discussion Starter · #7 ·
Also, i just put the new alternator in and it was charging fine. Started the jeep all was well. I shut the jeep down but left the key in the on position. I went into the house for a drink and came back out and saw smoke coming from the ignition module, you could hear if frying. This is the new module i installed with the alternator.
 

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i tried several different brands of modules and tried the ballast resistor, all kinds of bullshit, never figured out the problem, just dropped the money on the DUI setup and love it, cleaned up all the wires under the hood as well
 

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I had the exact problem with my 258 and painless harness. The guys at painless said no ballast resistor was required so I ran without one. After I fried my 2nd module I picked up a ballast resistor and everything was fine. It isn't a bad idea to make sure its mounted in a place where it won't overheat. For your setup it might not be a bad idea just to go straight to the MSD6a.
 

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I would check out the grounds on the engine. I had a customer come in the parts store that I work at and he was going thru modules in a few days. I asked him about his engine grounds and the other folks in the store looked at me like wtf is he talking about. Guy bought same type of module back found out the when engine was swapped out the ground straps didn't get hooked back up. Put them back on now he has gone several months with out a problem.
 
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