ECU question.

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RJK3

RJK3

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I'm replacing the /6 ECU with a V8 ECU, the /6 connector has 5 wires and the V8 ECU has 4 pins.
What do I need to do with the extra wire?
Also, what are the Ohm values I should see in the ballast resistor for MP chrome ECU?
Do I need to swap the voltage regulator as well?
Thanks for the help!
 
The older factory ECU's had 5 pins. The newer ones as well as the aftermarket replacements have 4. You can use a 4 pin in place of a 5 pin but not the other way around.

The 5 pin ECU requires the use of a dual ballast. The four pin ECU uses a single ballast. You can still run a dual ballast with the four pin ECU to look stock.
 
We don't know what model or year vehicle you have.

I should add that in most new 5-pin ECU's, the 5th pin is a dummy, thus doesn't even use the 2nd ballast. The coil ballast is ~0.5 ohm, but you can't accurately measure that, and the value changes greatly as it heats up. More important is the voltage at coil+ when running. I think ~8 V is correct. I never read of different ballast resistor values. Some later cars (80's?) used coils with "internal ballast". Don't use an external ballast with them. You should use an electronic Vreg. Most factory ones have a single triangle shaped connector. There are other models to retrofit older cars.
 
The car is a 73 Duster. I seem to recall reading somewhere that it was important to run the proper ballast resistor with the chrome ECU.
 
There may have been minor changes in ballast resistors, but no, not a special resistor for any one box that's considered "factory."

The deal is the older 5 pin boxes MUST have the older 4 pin resistor.


Newer 4 pin boxes CAN use either 2 or 4 terminal resistors. It's simply that the second half of the resistor now does nothing

You cannot tell a 4 pin from a 5 pin box by looking, because some boxes which are 4 pin actually have 5 physical pins. MOST if not all new boxes you buy nowadays will be (newer) 4 pin design

For a box to be a truely so called "chrome" box it must be a legitimate Mopar box. Aftermarket, replacement boxes usually and probably are not. They might be "chromed" on the outside, but that does not make them equivalent to the so called "chrome" box.
 
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