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Are you using relays on the fans etc?

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Let's try some troubleshooting instead of mud slinging.

If your ignition switch is from 1973 we are all wasting out time here as this is classic symptoms of a bad ign switch. OK????

Voltage tests should be done when the car is running.

When the car is running there should be 13.8-14.4 volts across the battery terminals and 7-9 volts at the coil. Period.

Pick a ballast resistor that puts the coil voltage at 9 volts.

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The previous ignition switch was about 6 years old and I just replaced it with a brand new one. Voltage drop across the switch is ~0.2V.

With the motor running with fans off, voltage is near 15V and with fans on, drops to around 14.2-14.4V or so. This translates to a volatge on the ignition side of the ballast of ~13.8-14V.

I think you are correct when you say the issue is the ballast. The ballast is only leaving 4.2V on the hi side of the coil once the fans are on. When you put the car in gear and the idle drops to ~700 RPM, the coil voltage starts falling below 4V and thats when the idle starts dying.

I have two ballasts on order with lower resistances. I will measure them when they arrive and fill everyone in on how they work!

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Ok first post on this problem .

Problem: engine dies after 15 mins. or so
Problem: haven't isolated the whats causing this.

Here's what I would do to isolate harness and ign. system .
Disconnect wires from + side of coil.
Run two wires from battery to + terminal on coil . one wire with an in line ballast resistor . start car and remove solid wire so you don't cook the coil
if the engine still dies, you have very little wireing and parts to look at ........
I would unhook your alt. just for the test .

Now if the engine still dies , your down to coil, ecm , dist and carb/fuel .
see what happens .

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I am thinking we **may** have found the issue when I saw that when the coil voltagge drops below ~4V the idle becomes rough and begins to lower which drops the voltage more and death spirals the motor.

With the fans on and in park the idle is about 800 RPM which keeps the coil voltage at 4.2V which is enough to keep her alive. Once I get below around 750, the alternator isn't keeping enougg voltage which begins this process.

I troubleshot the wiring and I am seeing voltage drop of almost 10V on the OEM ballast I have which is too much for my Blaster coil apparently.

I am guessing with the everything cooled off, I am right on the verge of too weak of a spark but the heat from the motor running may have pushed it over the edge raising resistance in the ballast/wiring.

Not sure why I ran OK before but this started about two months ago. Maybe I was just marginal the entire time and I just stepped over the edge?

I am hoping my theory here is correct as I have about troubleshot the hell outta this ignition system!

If this doesn't work, I will be trying your test along with others...

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...If you upgraded with a 100 amp alt you have to upgrade alt. wiring

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...If you upgraded with a 100 amp alt you have to upgrade alt. wiring

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Amen to that! This is a meltdown waiting to happen.

Rick

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I respectfully disagree! The way I have my fans wired, it is no more likely to "meltdown" than a factory setup.

I take the fan relay feeds directly from the alt stud so while the car is running, no fan current goes through the bulkhead/ammeter charging circuit! The only point where the 20 amp draw of the fans would go through the entire charge circuit is when it fulls from battery (car off). I doubt that a couple of seconds of 20 amp draw when the car is off would burn up the OEM wires which are all brand new in my case. :-)

Also a common misconecption is that a hi output alternator will push those extra amps through the charging circuit. The car/battery will only "take" what it needs (ohm's law). The only difference is that the hi output alternator will be able to "hold" a higher voltage given a lower resistance (more load/accessories ON) than the OEM 60 amp unit.

The issues where people are burning up their cars with hi-output units is where they tap into 12V power from the starter relay or battery terminal whitch DOES pull the extra current for those extra accessories (fuel pump/fans/etc) through the entire engine/dash harness while the car runs.

It also doesn't help if you have 40+ yr old wires and they are dirty and corroded....not to mention the factory didn't build much margin into the charging circuit as we all know.

Not a bad idea to upgrade the wiring but not necessary if wired/maintained correctly.

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I think 2 ohms is way too much. Also I seem to remeber the blaster 2 coil should use a .8 ohms resistor?

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According to the Mopar Performance catalog..
When using a Blaster coil, the correct ballast resistor value is 0.25 Ohms which is Mopar #P2444641.


Just my $0.02..

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When a fusible link blows it's gone. There is no reset to it just like a regular fuse.

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I think 2 ohms is way too much. Also I seem to remeber the blaster 2 coil should use a .8 ohms resistor?

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According to the Mopar Performance catalog..
When using a Blaster coil, the correct ballast resistor value is 0.25 Ohms which is Mopar #P2444641.

Good advice, take the 2 ohm resistor and pitch it.



Just my $0.02..

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