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I learn something new every day. Went to look at a potential parts van that the (original) owner is selling because he just no longer needs/wants to fool with it. Its an 85 150 passenger van 5.2/A999. The final straw was the engine just didnt want to stay running, said it would turn over and catch but as soon as the key was released from 'Start' it would die stone cold. Sounded like the classic ballast resistor failure had struck especially since he said he had never replaced it before. Went down to look at it and brought a spare resistor with me. Come to find out this thing had from the factory a 2 pin resistor and my 4 pin unit wouldnt plug in so we couldnt try it.

Is there anything special as to why this thing would have only had a 2 pin unit as original ? Stopped by the store the other day and picked one up for it and going through the options for an 85 they did list a 2 or 4 pin unit... I guess they dont have a big market for them cause the 2 pin unit was $2 more vs the 4 pin unit.
 

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As far as I know, it doesn't matter whether it is a 2 or 4 pin, it still does the same thing, it is just the wiring side to side, running through one resistor or two resistors on the back, essentially reducing the stress on the resistor wires it contains, unless someone else understands it or can explain it differently.
 

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I read someplace why they switched from a dual (4 pin) to a single (2 pin) ballast resitor at Chrysler. I can't remember the details and I can't find where I read it again yet.
 

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I believe the two resistors are different values, hence, it does matter whether it's 2-pin or 4, and how they are connected.
 

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I believe the two resistors are different values, hence, it does matter whether it's 2-pin or 4, and how they are connected.
That's correct, different values and different wire routing. I have a couple of diagrams, but they are on my desktop and I'm on my mobile right now.
 

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OK, I was able to find a little of the info on line. Mopar electronic ignition controllers had either 4 or 5 pins (although some 5 pin ones are really 4 pin ones as the 5th pin is a dummy).
If you have a 5 pin ECU, you must have the double ballast.
If you have a 4 pin ECU, you can have either a single or double ballast. Obviously simpler is better so once they switched over the the 4 pin ECU, the dual ballast went away.
What I read before explained it better so I'll keep looking.
 
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