Ok, so I had a mid-'70s chrysler ECU (5-pin) on my '66 Dart, and I was recently given a brand new orange box (4-pin). My question is about what is going on at the ballast resistor (currently has a dual ballast resistor)?

From the orange box:
-green wire is unused
-light blue wire goes to one prong on single ballast resistor
-black goes to coil (-)
-two cables to the dizzy

Also I have one cable from the coil (+) to the other prong on the ballast resistor.

So what about the two connectors that came off the dual ballast resistor? Where do they go? What are they? Each of the connectors has two cables on it, are these connected to the start and run circuits, and if so will I have to splice them or could I use one or two double male, single female adapters? A pictures of such a conversion would be much appreciated!

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'66 Dodge Dart

The conversion is to bolt the new box in place making sure it's well grounded. That's all you have to do to run the car with a 4-pin module. If you want to remove the wiring associated with the 5th pin and 2nd element of the dual ballast resistor you may, and you may also substitute a single ballast resistor, but it's not required.

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Joshua

Wow, thanks for the great info Josh!

I have a new ECU harness and I'm going to be using it since my old one is falling apart. So I can just clip that wire and not worry about my dual ballast resistor looking odd with 1 prong being bare?

Also, what needs to happen to switch some of my wiring to a single resistor setup (I still have 3 out of 4 prongs on the dual resistor in use, do I double up on 1 of the prongs from a single ballast resistor)?

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'66 Dodge Dart

I think I got it...

Remove the two wires on the dual ballast resistor that come from the 5-pin ECU. Use a 3-sided terminal adapter (2 male, 1 female) to plug the blue ECU wire into the same terminal as whichever set of wires are connected to the ignition on circuit. Is that all correct?

This all seemed much more difficult when (over-)thinking about it...

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'66 Dodge Dart

This might help:

http://www.slantsix.org/articles/elect_ ... wiring.htm

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Chuck Rivers, Webmaster

Thanks Chuck, was looking all over for that, didn't realize it was in the articles section. It all makes sense now.

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'66 Dodge Dart

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Chuck Rivers, Webmaster

hi guys! i had an experience that i have checked my ignition wire set with a multimeter and for some reason I am getting no voltage at all. Any ideas what the problem could be?

When people say ignition wires they usually mean the high voltage spark plug wires, but perhaps you're referring to the low voltage "primary" wiring - let me cover both and I apologize if I'm telling you things you already know.

When you're actually not making a spark, the voltage in the HV spark plug wires is zero; when you're actually making a spark, it is -5000 to -25000V depending on many factors.

The only thing you can do with a multimeter is check the HV wires is to check their resistance (with the ignition off!). If a wire has infinite resistance (way beyond 10-20Kohms/foot of length), it's mostly probably bad, but a proper resistance does not tell you that it is good. You probably need set your meter on the highest resistance scale.

If they all read infinite, you probably have a problem using or inside your multimeter - check it against something like the HV connection of the coil to the - post; that's typically 5-15Kohms.

On the low voltage (primary) side, the wires that feed your + and - coil connections may have voltage or not depending on the design of the ignition system you're using. For the standard (4 or 5 pin) Mopar electronic ignition, with the system turned on but not firing nor cranking, you ought to see something like 6-8V on the + coil and 0.5-1V on the -coil post. For the point system you usually see +6-12V on the + post and either the same as the + post or 0V on the - post: usually, the car stops with the point closed so you have +6-8V + and 0V -, but it can stop with the points open so you have +12V on both.

If you have the ignition on and no voltage at the coil, check for voltage at the ballast - it ought to have +12V on one side and the same as the +coil on the other. If you have 12V going to the ballast and nothing out, you've probably got a broken ballast. I always carry a spare. If you don't have voltage there, there are 2 common failure points to check next.

First, I'd look at the bulkhead connector. The pins there often corrode a bit, get hot, and then rapidly get worse and melt the surrounding plastic. The next spot I'd check is the connector that feeds the ignition switch - often oxidation there also causes the same symptoms.

Good luck.