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Ballast Resistor for Mopar ECU Orange Box? #2709810
10/24/19 02:28 PM
10/24/19 02:28 PM
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I've read many posts on this subject with discussions and opinions all over the place. Even though I don't have points, I want to offer some protection to my stock coil and ECU orange box, but also want to get a good spark while maintaining the factory ballast resistor look (ceramic block with metal strap). Does anyone make a BR with lower ohm resistance that looks close to factory correct? I'm only getting about 5.5 - 6 volts to my coil with an old, original BR and would like to maybe get the voltage up closer to 9 volts.


1971 340 Challenger Conv. PACE CAR
1970 440 Six Pack Challenger 4-speed Dana
1972 Duster 340 4-speed Lemon Twist Survivor
1970 U-Code Challenger R/T, Triple Red, 4-Speed, Dana
1969 Talladega Torino, 428CJ
1969 Gurney Cyclone Spoiler II, 351 4 BBL
1971 Demon w/440, 10.70s @125 MPH Street Legal!



"Id rather have a bottle in front of me than a frontal lobotomy" Ben Franklin 1755
Re: Ballast Resistor for Mopar ECU Orange Box? [Re: RSI700VIPER] #2709853
10/24/19 06:08 PM
10/24/19 06:08 PM
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You could get creative and gut an original resistor and soldier a wire from terminal to terminal and basically loose nothing. You can lightly blast the resistor, soak the collar in evaporust and then matt clear it and you have a really nice looking piece. twocents


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Re: Ballast Resistor for Mopar ECU Orange Box? [Re: RSI700VIPER] #2709864
10/24/19 06:44 PM
10/24/19 06:44 PM
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Mattax Offline
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Originally Posted by RSI700VIPER
I've read many posts on this subject with discussions and opinions all over the place. Even though I don't have points, I want to offer some protection to my stock coil and ECU orange box, but also want to get a good spark while maintaining the factory ballast resistor look (ceramic block with metal strap). Does anyone make a BR with lower ohm resistance that looks close to factory correct? I'm only getting about 5.5 - 6 volts to my coil with an old, original BR and would like to maybe get the voltage up closer to 9 volts.


First thing would be to check the possible reasons for the voltage you're seeing.
The voltage on the coil side of the resistor will depend on the voltage on supply side (ignition).
So that's probably the first thing to check. Check it while the engine is running at idle and off idle - say 1250 rpm. At the same time check the voltage at the alternator output stud.

The voltage drop across a resistor will depend on the current running through it. So if for some reason the coil is drawing a lot of current, that's another possible reason.
Chrysler resistors should be checked for resistance at ambient temperature but were expected to have higher resistance when warm (low speed driving) and cool down a bit at higher speed (resulting in slightly lower resistance).
.
If you are measuring .5 to .7 ohms, that's about right for most factory combinations.
Check the coil primary resistance too. That can affect the current draw and therefore was matched with the appropriate resistor.

Supplying higher voltage to the coil may or may not increase spark energy.
Higher voltage can be useful when there isn't time for a coil to get saturated before firing. Otherwise its just heating the coil up.

Re: Ballast Resistor for Mopar ECU Orange Box? [Re: RSI700VIPER] #2709873
10/24/19 07:29 PM
10/24/19 07:29 PM
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RapidRobert Offline
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the P2444641 has a nominal ohms of .25 ohm. the P5206436 is 1 ohm nominal, (likely higher on both of these new), My last point ballast ohmed at 1.6 ohms. You could swap the metal holder for a more OE appearance tho those the white bakelite material should be pretty identical in appearance.


live every 24 hour block of time like it's your last day on earth
Re: Ballast Resistor for Mopar ECU Orange Box? [Re: Mattax] #2709875
10/24/19 07:43 PM
10/24/19 07:43 PM
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Originally Posted by Mattax
Originally Posted by RSI700VIPER
I've read many posts on this subject with discussions and opinions all over the place. Even though I don't have points, I want to offer some protection to my stock coil and ECU orange box, but also want to get a good spark while maintaining the factory ballast resistor look (ceramic block with metal strap). Does anyone make a BR with lower ohm resistance that looks close to factory correct? I'm only getting about 5.5 - 6 volts to my coil with an old, original BR and would like to maybe get the voltage up closer to 9 volts.


First thing would be to check the possible reasons for the voltage you're seeing.
The voltage on the coil side of the resistor will depend on the voltage on supply side (ignition).
So that's probably the first thing to check. Check it while the engine is running at idle and off idle - say 1250 rpm. At the same time check the voltage at the alternator output stud.

The voltage drop across a resistor will depend on the current running through it. So if for some reason the coil is drawing a lot of current, that's another possible reason.
Chrysler resistors should be checked for resistance at ambient temperature but were expected to have higher resistance when warm (low speed driving) and cool down a bit at higher speed (resulting in slightly lower resistance).
.
If you are measuring .5 to .7 ohms, that's about right for most factory combinations.
Check the coil primary resistance too. That can affect the current draw and therefore was matched with the appropriate resistor.

Supplying higher voltage to the coil may or may not increase spark energy.
Higher voltage can be useful when there isn't time for a coil to get saturated before firing. Otherwise its just heating the coil up.


Mattax - How do I check coil primary resistance? Also, with all things checked out and operating normally, what voltage should I see at the coil with engine idling?


1971 340 Challenger Conv. PACE CAR
1970 440 Six Pack Challenger 4-speed Dana
1972 Duster 340 4-speed Lemon Twist Survivor
1970 U-Code Challenger R/T, Triple Red, 4-Speed, Dana
1969 Talladega Torino, 428CJ
1969 Gurney Cyclone Spoiler II, 351 4 BBL
1971 Demon w/440, 10.70s @125 MPH Street Legal!



"Id rather have a bottle in front of me than a frontal lobotomy" Ben Franklin 1755
Re: Ballast Resistor for Mopar ECU Orange Box? [Re: RSI700VIPER] #2709882
10/24/19 08:06 PM
10/24/19 08:06 PM
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RapidRobert Offline
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put your ohmmeter on 20 ohms & touch the 2 primary coil terminals with the leads, with the engine harness wires disconnected from the coil terminals. EDIT This is for coil primary (cold) ohms not coil running voltage

Last edited by RapidRobert; 10/24/19 08:09 PM.

live every 24 hour block of time like it's your last day on earth
Re: Ballast Resistor for Mopar ECU Orange Box? [Re: RSI700VIPER] #2709909
10/24/19 10:39 PM
10/24/19 10:39 PM
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Phila. Pa.
Mattax Offline
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Measure across the + to -
1973 Dodge FSM shows two coils. one with primary reistance of 1.6 - 1.79 ohms and the other 1.41 to 1.55 ohms
The compensating ballast reistor should be .5 - .6 ohms at 70-80*F
1969 is the same. So no change there.

The voltage at the coil depends on conditions, that's why its best to measure the voltage going to the resistor.

Re: Ballast Resistor for Mopar ECU Orange Box? [Re: Mattax] #2709912
10/24/19 11:16 PM
10/24/19 11:16 PM
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Mattax Offline
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If your interested in how this stuff works Chrysler's master tech conference is a great start.

Ignition
http://www.imperialclub.com/Repair/Lit/Master/259/Page03.htm
and how the electronic version works.
(note: the orange box and other later ECUs only have 5 pins and doesn't need the 5 ohm resistor to regulate operating current)
http://www.imperialclub.com/Repair/Lit/Master/292/page04.htm

Re: Ballast Resistor for Mopar ECU Orange Box? [Re: Mattax] #2709939
10/25/19 07:59 AM
10/25/19 07:59 AM
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NW New Jersey
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RSI700VIPER Offline OP
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Originally Posted by Mattax
If your interested in how this stuff works Chrysler's master tech conference is a great start.

Ignition
http://www.imperialclub.com/Repair/Lit/Master/259/Page03.htm
and how the electronic version works.
(note: the orange box and other later ECUs only have 5 pins and doesn't need the 5 ohm resistor to regulate operating current)
http://www.imperialclub.com/Repair/Lit/Master/292/page04.htm


Anyone who considers themself less than proficient on the nuts and bolts of a Chrysler ignition system should read these articles. Thanks Mattax.


1971 340 Challenger Conv. PACE CAR
1970 440 Six Pack Challenger 4-speed Dana
1972 Duster 340 4-speed Lemon Twist Survivor
1970 U-Code Challenger R/T, Triple Red, 4-Speed, Dana
1969 Talladega Torino, 428CJ
1969 Gurney Cyclone Spoiler II, 351 4 BBL
1971 Demon w/440, 10.70s @125 MPH Street Legal!



"Id rather have a bottle in front of me than a frontal lobotomy" Ben Franklin 1755
Re: Ballast Resistor for Mopar ECU Orange Box? [Re: RSI700VIPER] #2710003
10/25/19 01:00 PM
10/25/19 01:00 PM
Joined: Feb 2010
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Mattax Offline
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up Thanks!
They have almost the whole series there.
http://www.imperialclub.com/Repair/Lit/Master/
I don't know how much longer it will be around.
Imperialclub.org was the mirror site I always went to, and the links stopped working last month.
I tried to e-mail them and it failed to go through. shruggy

Just noticed your location. I was working up that way 'til last year. Would usually go through Blairstown - we were based out of Camp KEP if you know the old scout camps.

Re: Ballast Resistor for Mopar ECU Orange Box? [Re: Mattax] #2710830
10/29/19 03:15 AM
10/29/19 03:15 AM
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383man Offline
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The normal voltage reading at the coil + terminal with the key on eng not running is usually around 7.5 volts when going through the ballast. As said most of the stock ballast I have seen were from about .5 ohms to about 1 ohm. Myself I have .25 , .50 , .75 and 1 ohm ballast laying around in my garage I have got over the years. If you try to read the voltage at the coil + terminal with the eng running its not an accurate reading because its just an average of the coil primary when grounded and ungrounded. When ever the coil primary is ungrounded (coil firing) you will read 12 volts (battery volts) because the circuit is not flowing to ground at that time and then when the coil primary is grounded it will read around 7 volts or so. That's why its best to read the coil volts with the key on eng not running at the coil + terminal which should be around 7.5 with the proper ballast but it will vary the longer the key is on as the ballast will get hotter and drop the voltage some. I run the orange MP ign ECU on my 63 and I don't use any ballast as I run a full 12 volts to the coil but I use the Accel super coil and it works good with no ballast because of the primary resistance in the super coil. I have been running my car about 5 years like that now but with a stock coil I would use a ballast with it. Depending on the coil and year car as to the exact ballast it calls for as the factory service manual will tell you. But I would shoot for around 7.5 volts checking at the coil + terminal with the key on eng off and check it as soon as you turn the key on so the ballast don't get to hot. If you get that then with the eng running at higher speeds the voltage at the coil will be a bit higher since the ballast will be cooler since the primary circuit has less time grounded at higher rpm and the ballast cools some and has less resistance when cooler and the coil voltage will go up some. Ron

Last edited by 383man; 10/29/19 03:17 AM.
Re: Ballast Resistor for Mopar ECU Orange Box? [Re: 383man] #2711027
10/29/19 07:44 PM
10/29/19 07:44 PM
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calrobb2000 Offline
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hi ,

i have also ran my 73 cuda with the accel super coil and no resistor for years , but i tried it on my 69 valiant and the super coil got soo hot it cooked the oil out of the coil ?

soooo ????

Re: Ballast Resistor for Mopar ECU Orange Box? [Re: calrobb2000] #2711100
10/30/19 06:23 AM
10/30/19 06:23 AM
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383man Offline
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Originally Posted by calrobb2000

hi ,

i have also ran my 73 cuda with the accel super coil and no resistor for years , but i tried it on my 69 valiant and the super coil got soo hot it cooked the oil out of the coil ?

soooo ????


That's a test I do and I did on mine when I took the ballast out of mine with the super coil and orange MP ECU. I let the car run about 15 minutes and then drove it for over a 1/2 hr and then lifted the hood and felt the coil. I knew if it was real hot it I would not like that and would put the ballast back in but it was so cool that I was surprised to see my ign coil that cool after 45 minutes of running time. I had heard of guys running MP ign ECU's and no ballast and I figured I would try it. And I have now been running my 63 like that with the MP orange ECU and the Acell super coil and no ballast for about 5 years. Ron

Last edited by 383man; 10/30/19 06:24 AM.
Re: Ballast Resistor for Mopar ECU Orange Box? [Re: 383man] #2711166
10/30/19 09:43 AM
10/30/19 09:43 AM
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jlatessa Offline
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Ron, could you Ohm the resistance values on your Super Coil?
I want to see how it compares with the one we have on the shelf as we're using the older orange box too.

Thanks, Joe

Re: Ballast Resistor for Mopar ECU Orange Box? [Re: jlatessa] #2711591
10/31/19 11:19 AM
10/31/19 11:19 AM
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GomangoCuda Offline
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This subject has been debated here dozens of times. Neither side will ever accept the others explanation. Years ago I posted information I found about what the total resistance (coil primary + ballast resistor) should be to match the transistor. But I don't remember what it was or who the source was confused shruggy. It might be in one of the race manuals from D.C. or M.P.

Personally I have been running a Supercoil for about 18 years with a .8 resistor and a chrome box. No issues.

I don't really have anything else to add except -
"In theory, there is no difference between theory and practice. In practice, there is."

Do what works for you.


In theory, there is no difference between theory and practice. In practice, there is.
Re: Ballast Resistor for Mopar ECU Orange Box? [Re: GomangoCuda] #2711594
10/31/19 11:30 AM
10/31/19 11:30 AM
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I too ran a supercoil with no ballast & no issue & accel want .7 ohms with it. I would stay conservative & carry a spare


live every 24 hour block of time like it's your last day on earth
Re: Ballast Resistor for Mopar ECU Orange Box? [Re: jlatessa] #2711723
10/31/19 07:24 PM
10/31/19 07:24 PM
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Originally Posted by jlatessa
Ron, could you Ohm the resistance values on your Super Coil?
I want to see how it compares with the one we have on the shelf as we're using the older orange box too.

Thanks, Joe


Yes I will try to go out in the garage tomorrow and check it. Ron

Re: Ballast Resistor for Mopar ECU Orange Box? [Re: GomangoCuda] #2711724
10/31/19 07:35 PM
10/31/19 07:35 PM
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Originally Posted by GomangoCuda
This subject has been debated here dozens of times. Neither side will ever accept the others explanation. Years ago I posted information I found about what the total resistance (coil primary + ballast resistor) should be to match the transistor. But I don't remember what it was or who the source was confused shruggy. It might be in one of the race manuals from D.C. or M.P.

Personally I have been running a Supercoil for about 18 years with a .8 resistor and a chrome box. No issues.

I don't really have anything else to add except -
"In theory, there is no difference between theory and practice. In practice, there is."

Do what works for you.




Well you are right as it boils down to the total primary resistance of the primary circuit as to how many amps will flow in the primary circuit. To many can overheat the coil and ECU. To little and could be a weaker spark. But I agree its the coil primary resistance that can determine what ballast of what ohms will work to give good spark and not overheat the coil or damage the ECU. I did run a .5 ohm ballast in my ign but since I kept hearing about many running Mopar ign with no ballast I decided to try it with my super coil. Course I carry and extra coil and ECU just in case and it ended up working fine with the super coil. It may not work with some other coils as it depends on the ohms of the coils primary circuit to start with. But since I race my car sometimes and jet it for mph at the track I like a hot spark to help keep my plugs clean and that's why I decided to try it with no ballast and found out my setup works good with no ballast. Course it will boil down to total primary ign circuit resistance to have the right amps flowing and not damage the coil or ECU and produce the right spark. I happen to find one setup that's works good for me and gives a good strong spark and don't hurt any ign parts. Ron

Last edited by 383man; 10/31/19 07:37 PM.

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