Correct ballast resistor for standard to electronic conversion

[HALIFAXHOPS]

They are all over the place (ballast values) You probably can never go wrong with a 1 ohm for all but a .25 might fry a box, really not positive like posted earlier there are no schematics on them to investigate.

 

[66Satellite47]

Is that a P3690256?

Yes

 

[66Satellite47]

To be absolutely assured and definitive of which ECU (blue vs orange box) is better, I would want to see a schematic diagram of the internal components and connections. This is NOT how the ECU, resistor, coil, and distributor pick up coil is connected BUT what is inside the ECU box. I'm sure my request would be ignored by the manufacturer unless l could perform a autopsy of a failed box and determine a root cause failure analysis.
BOB RENTON

I'm certain the internal component differences are what make the difference between a Mopar Orange box & Blue box (3690256). The coil & ballast resistor must match the ECU internal components & circuitry. I was just saying my observation was that the Blue box would outperform the Orange box at the drag strip. And the combination of the parts should match the manufactures recommendations (wiring diagrams & components).

 

[HALIFAXHOPS]

The orange is rated to 6000 and the blue to 7500/9000 with a certain ballast resistor according to the chats I posted. They came from a MP book so I would think it is right.

 

[Daves69]

.....unless l could perform a autopsy of a failed box and determine a root cause failure analysis....

Evidently there are plenty of "orange" failures out there. Someone must have a "real" Chrysler P4120505 orange that has failed they could send ya' to RE.
Haven't seen many of the P3690256 mentioned though, that's why I asked 66Sat about. Might be a harder find to compare unless maybe Ray has one laying around.

 

[Ranger16]

I'm sure my request would be ignored by the manufacturer unless l could perform a autopsy of a failed box and determine a root cause failure analysis.
BOB RENTON

I was just about to pitch my orange box that failed, but if you want to do an autopsy, I'll send it to you Bob.

 

[RJRENTON]

I was just about to pitch my orange box that failed, but if you want to do an autopsy, I'll send it to you Bob.

Sure....upon receipt, I'll try and remove the potting compound without destroying the circuit board, and individual parts....thanks for the offer. Ill send you a PM with my contact information....
BOB RENTON

 

[66Satellite47]

Evidently there are plenty of "orange" failures out there. Someone must have a "real" Chrysler P4120505 orange that has failed they could send ya' to RE.
Haven't seen many of the P3690256 mentioned though, that's why I asked 66Sat about. Might be a harder find to compare unless maybe Ray has one laying around.

Dave, the P3690256 is so old, but a really good piece for a new racer on a budget. Mine is still on the shelf complete, it ran great & I'd trust more than the current bunch of ECU's. I have the ECU, ballasts, coil & a DC distributor that's nearly new. Old stuff but sure worked. Only disadvantage is no rev limiter.

 

[Ranger16]

Sure....upon receipt, I'll try and remove the potting compound without destroying the circuit board, and individual parts....thanks for the offer. Ill send you a PM with my contact information....
BOB RENTON

It's on it's way to you Bob. I'm sure we'll all be interested in your findings.

Just for reference it is about 5 yrs old with about 8,000 miles on it.

 

[Bee1971]

Orange Box
https://www.forbbodiesonly.com/moparforum/threads/whats-in-the-orange-box.157220/
https://www.forbbodiesonly.com/moparforum/threads/whats-in-the-orange-box.157220/


Fail , as in no start is one thing - Dead

However

I put my 2001 Mopar Performance Chrome back on today for comparison

Starts and idles awesome - Low and mid awesome

5,000 RPMs , like a rev limiter kicks in
Would love to know what fails on that circuit board at RPM

 

[Daves69]

Orange Box
https://www.forbbodiesonly.com/moparforum/threads/whats-in-the-orange-box.157220/
https://www.forbbodiesonly.com/moparforum/threads/whats-in-the-orange-box.157220/

My old P3690256 Blue box is a little different from Twecomms Orange. I imagine updates (Lol, cost cutting) to the Oranges were made over time. The old 5 pin Black box to the left was sitting in a box with this Blue box on a garage shelf "self leaching" over the years BTW........

 

[66Satellite47]

Forgot about the 2018 Orange box thread, it is real good. Too many folks took the Orange box as a "race" ignition. It's not, it's a great upgrade for a mostly stock street motor that is not expected to go past about 5500 Rpm. Blue box & then the MSD's were intended for 6500+ RPM. Lots of "Orange box" clones out there. Off shore stuff?

 

[MoparGuy68]

I have cleaned up the "REAL" MP P4120505 Orange box that came with my car's extra parts. It is made in USA, and I'd prefer to run it on my car rather than the "made in CHINA" box that was in it when I bought the car. I had a USA MP Orange box on my Challenger from 1989 to 1998, and never had a problem with it..

The ballast resistor that was on the car is a 1.25 Ohm, single type, closed back, that I have tested at 1.25 Ohms. The other two single resistors are marked 0.8 Ohms and test at 0.8. The dual resistors, one tests at 5 and 1.25 Ohms, while the other tests 6.25 and 1.25 Ohms (this second looks to be bad at 6.25).

The Chrysler voltage regulator included with the parts is also marked made in USA. Look how much nicer the firewall looks with a genuine USA Orange box and voltage regulator. Instead of the China box and Ford regulator.

 

[MoparGuy68]

Really depends what box you are running actually. Hope this helps.

View attachment 987637 View attachment 988398
Most use the 1.2 ohm ones. Check the value if you are using the single one. They can not be 1.2 They also have them in other values. You can see that in the chart.

So, with a P4120505 Orange ECU, and a Mopar 2495531 Coil, should I be using a 0.7 Ohm resistor? Is my coil the correct coil to use with a P4120505 box?

 

[MoparGuy68]

I can test your ecu just the rides. Easy with a bench tester.

What kind of bench tester do you use to test the Chrysler ECUs? I've seen plenty of used ECU testers (one unit for all ECU types, Ford, GM, Chrysler etc), but they seem to have Chrysler harnesses that are designed for testing the 1970's 5 pin ECUs and lean burn ECUs (late 70s).. Are you using the same test device for both 4 and 5 pin ECUs?

 

[Ranger16]

I had a USA MP Orange box on my Challenger from 1989 to 1998, and never had a problem with it..

That is the exact same box that failed on me after 5 yrs/8000 miles. that I just sent to Bob Renton for an autopsy. It's odd that one will last so long and the next fail so soon. In the words of the eloquent Kelly Bundy, "It makes the mind wobble".

 

[Bee1971]

Dunnick Racing did a lot of testing on coils and ECUs

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/1230955/1.html

https://www.hotrod.com/articles/mopp-1211-3-2-1-ignition-box/

 

[66Satellite47]

Dunnick Racing did a lot of testing on coils and ECUs

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/1230955/1.html

https://www.hotrod.com/articles/mopp-1211-3-2-1-ignition-box/

One point, with the Mopar boxes, the coil should match the box. I think both durability & performance are affected by the compatibility. Also I'm 99% sure that the coil used with the Mopar Blue box 3690256 race ECU was a specific Accel round coil not the "off the shelf" chrome coil. Same true for MSD style boxes, coil characteristics need to match the box circuitry needs.

 

[383man]

I can tell you that I ran a MP orange ECU unit for at least 5 years using the old yellow Accel Super Coil and no ballast at all. I had heard some do this so I tried it since I carried spare ECU's and coils in my car. It worked fine and the coil never got hot. And I pushed that box to 6500 rpm and my car never missed a beat. I bought that box around 1999. I originally ran it with a .5 ballast but as I said about 5 years ago I bypassed to ballast and put the full 12 volts to the Super Coil. The Super Coil must have the right primary resistance to work good in that setup. And even after driving the car an hr the coil never got hot at all so I knew it was not overheating and the orange box handled it fine. Course its not what Mopar says to do but I had a few guys like my brother running a ful 12 volts to the coil and using the orange and silver boes and working for them so thats why I gave it a try and it worked good. But that may not work using a stock coil as I would still use the proper ballast with a stock type coil. Ron

 

[HALIFAXHOPS]

What kind of bench tester do you use to test the Chrysler ECUs? I've seen plenty of used ECU testers (one unit for all ECU types, Ford, GM, Chrysler etc), but they seem to have Chrysler harnesses that are designed for testing the 1970's 5 pin ECUs and lean burn ECUs (late 70s).. Are you using the same test device for both 4 and 5 pin ECUs?

Zetron IMT 1000 Is my go to. I have had the mopar testers also but prefer this one. Same ast the parts stores used to have. It tells you what failed internally. Also does most domestics 72 to 84.

Same as the one I use.