Bad Coil?

Bee1971 said:

How was the wiring harness ends that connect to the Ballast Resistor itself

Just you removing the wiring from the old to new resistor could have been enough to cause a connection for voltage to the positive side of coil

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Red63440 said:

Let me ask this, what happens if you use a regular coil instead of one made for electronic ignition, the answer may help to explain the problem.

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RJRENTON said:

With the correct ballast resistor, in normal operation, the resistor runs extremely HOT. It is very possible that because of the heat generated, that the resistor's internal connections to the male wiring harness connectors have become oxidized possibly causing the "no start when hot" condition. Since you have replaced the resistor with a spare, has this fixed the problem?
BOB RENTON

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Bee1971 said:

Chrysler used the SAME ignition coil with electronic ignition thru 1978 as it did with points systems earlier , like from the 50s and 60s

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moparedtn said:

Thanks, that gets me halfway there. Now, what was the rating of the factory ballast on the Mopar electronic
ignition?

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HALIFAXHOPS said:

Just a FYI Make sure the ballast resistor has the proper ohm rating they have them from .25-1.5 ohms and all look pretty much the same in the two pin. Four pin are always right out of any box. .5/1.2 ohm that I have seen.

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Bee1971 said:

Like Hops listed
Factory Dual Ballast Resistor
.5 OHM on the Ballast Resistor for the Positive side of Coil in the run position of ignition switch
The other side of the Ballast Resistor was for the fifth pin on the ECU/Ignition Module
Was typically a full 5 OHMs on that side of resistor
That’s why Chrysler inserted pins on there wiring harness connectors and put holes in there Dual Ballast Resistor
So you couldn’t reverse the wiring connectors by accident and flip the OHM Resistance which would have damaged the ECU/Ignition Module going thru that fifth pin
Trying to find a .5 OHM Resistor in the Factory Dual Ballast Resistor is next to impossible for the positive side of coil
All after market Dual Ballast Resistors are in the 1.2 OHM to 1.8 OHM Resistance on the positive side of coil
If you can find a Factory correct Mopar part # 3656199 Dual Ballast Resistor
It will have an open back on that side of resistor exposing the element
And have the part # stamped in the Front of Resistor in the porcelain
And will BEE rated at .5 OHM
Anyways if you want to run a Single Ballast Resistor
Almost 100% of Chinese / Mexican ECU/Ignition Modules only run 4 pins
That’s why you can get away with a single side Ballast Resistor - And you have much more easier choices of OHM Resistance values in all shapes
.25 OHM all the way up to 1.8 OHM
FACTORY CORRECT IS .5 OHM RESISTANCE on the Positive Side Ignition Coil
Are we confused yet
I need my coffeee eeeeee

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moparedtn said:

Thanks for the reply and yes, HH is always a great help in all things electrical - and that chart is well known,
of course - but it doesn't really help when it lists several different impendences for the same ECU, nor for
different coils with the same this or that - not to mention, there's no years or engine applications listed, either.
I always took that to mean you had a window of acceptable ballasts for those same units, since that's what
the chart indicated....not much help when you want to know what MOPAR actually sold in the conversion kits.

Yes, I'm making a big assumption that what Ma sold was correct out of the box here, but I'll go with it if I can
find out what the heck it was...
And by the way, the Mopar "performance electronic ignition conversion kits" used a single ballast and in the
instructions, it specifically says how to wire a car that had a dual ballast to it, that those were "unnecessary".
I've got a copy of the installation instructions for the old kits (well, the ones being made in the late 70's,
anyways) in PDF format that I could probably copy/paste into a large post on here if anyone would like
to see it.
Unfortunately, it does not specifically list individual kit components by part number (or by rating, in the case
of the ballast). I have been told by a couple folks who should know that the ballast in those kits was 0.8ohm
rated - it would just be nice to know for sure.

Another thing that interests me is the reference by more than one that we must use a coil made specifically
for electronic ignitions, when I just saw again that Ma didn't change coils from the 60's on to 1978??
Same coil, whether points or ECU eh?

As an aside, I've been playing around on the Standard Ignition website (great source of info since 1919!)
For my 1968 (standard points), it shows for a stock ballast:
Part # RU-4 (single ballast)
Cold Resistance:0.5-0.6 ohms
Operating Resistance:1.75 ohms
(It shows similar through 1972)

For a 1974:
Part # RU-14 (dual ballast)
Cold Resistance:1.15-1.38 ohms
Operating Resistance:4.75-5.75 ohms At 25 Degrees C

So I gotta think the ballast change-over mandated in the Mopar conversion kit is significant??

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Sixpactogo said:

All that pretty white paint on your inner fender where you orange box is mounted is probably causing all of your woes. If that box doesn't have a less than .05 ohms from the case to neg post on the battery, it will get hot and open up until it cools down. Happens all the time. Paint is not a good ground. I hear guys whining about the orange box failing when more than likely was too much paint under the mounting screws.

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