No ballast resistor needed with 12v aftermarket coil?

[James E Vining]

If I run a aftermarket Coil I would no longer even need the ballast resistor since the coil would now be a 12V unit not the 6V which is what the coil gets?

[MotorPro]

The purpose of the resistor is to stop the points from burning up. Many high performance aftermarket coils actully require a second resistor.

[James E Vining]

Ok so I accidentally started talking about this post in my other post sorry about that.
Ok so I do not have Points so no issue there (Swapped over to electronic) Found newer ECU's have went to 4 pin only and have eliminated the Lower Voltage Wire/Pin.
As to teh aftermarket coils, Some of them require a Separate ballast resistor?? SO the do not run on 12 V either?
I assume if a person buys a aftermarket coil and it needs a special ballast resistor it would state so or possibly come with one?
If my coil states 12 V on it should I be running 12 V to it?
I do not know if it is a aftermarket coil of some sorts as this Winne was Given to me in 2008 and the guy who had it knew nothing at alll about it.
I mean nothing

[DaveVA78Chieftain]

For Dodge based ignition systems the ballast resistor is used on both points based AND Electronic ignition based systems.

Please refer to page 6 (http://www.imperialclub.com/Repair/Lit/Master/312/page06.htm) of the Chrysler Master Mechanic Training Publications Electronic Ignition Troubleshooting: http://www.imperialclub.com/Repair/Lit/Master/312/cover.htm for a description of how the dual ballast resistor is used.

If memory serves me correctly, it is only the "Gold ECM" high performance versions that use only 4 pins.  Most all stock MOPAR setups used the 5 pin ECM setup (All motorhome versions).

Unless the aftermarket coil documentation specifically states to not use a ballast resistor, then normally a ballast resistor is used unless you are using a replacement ignition system (i.e MSD) that does not require it.

Please refer to http://www.classicwinnebagos.com/forum/index.php/topic,7603.0.html for other OEM information used in the Motorhome applications.

Dave

[James E Vining]

Hey thanks, Hmm I wonder if I got a High performance Version from Autozone, it was only $19.99 so I find that hard to believe but  weirderd things have happened to me.

[James E Vining]

I went a looked at the ECM (Electronic Control Module) I was calling it a ECU as I somehow thought that was it's name thanks for helping me with that, anyway The #3 Pin is missing on mine which goes to the aux 5 Ohm Side of the ballast Resistor and is the J4-18DG wire and according to the wiring diagram the only other wire that has Power from battery is the J10C-18RE which looks like it is Direct 12 V no ballast Resistor.
I noticed something new today as I was running it when it was sitting Ignition on but not running I was getting about 6.5 V at the coil and as it set it seemed to keep dropping but when I started it it jumped to about 7.5 V then when I was running it at 3K it was around 9.5 V .
I assume as it heats up it gains more resistance and when the engine is running it cools off and resistance drops?
.

[DaveVA78Chieftain]

The coil is turned on and off for every cylinder firing therefore the coil voltage is actually a pulsating (AC) signal.  As the ON/OFF frequency increases due to RPM increassing, the effective voltage at the coil increases.  Has nothing to do with heat.

Dave

[PwrWgnWalt]

Addition to an old thread, in case anyone refers to it later...

12V or 6V stamped on the coil refers to the vehicle's chassis/frame/starter electric system power - you need a 12V coil if you use a 12V battery (and a 6V coil if your chassis/starter uses only a 6V battery - these are usually much older vehicles).

The earliest ECU's (Mopar Electronic Control Unit) from 1972-1979 all had 5 pins (from the factory) and all pins were used. These must use the dual ballast resistor (our Motorhomes), at 1.0 Ohm (+/- 0.5 Ohm)  (Normal, or 'Run'), and 5.0 Ohms (Auxiliary, or "Start").  The Auxiliary circuit (5.0 Ohms) fed the pin not used later (as that circuit was made internally inside the 4-pin ECU's). 

The later ECU's used [/font][/size]only 4 pins. Many (most/all?) of the replacement ECU boxes available today use only 4 pins (e.g., the Mopar Performance "Orange Box").  The 5-pin harness can connect right to the 4-pin ECU with no issue. These 4-pin ECU's don't really need the 'Auxiliary' circuit of the Dual Ballast Resistor, but many folks just leave the wiring alone - and that's OK. With a 4-pin Electronic ignition ECU, you could use a single ballast resistor from 0.5-1.4 Ohms.  Some suggest you don't have to use a ballast resistor at all with a 4-pin ECU... but admit the life of the coil will be shortened.

With points, you really should use a Ballast Resistor of some sort (may be coil-specific), or you will likely burn the points in addition to shortening the life of the coil.  The stock Mopar points-ignition uses a single resistor (two prongs) at about 0.5 Ohms (+/- 0.1 Ohms).I would suggest you should use a Ballast Resistor with any coil that does not already have one built-in. Depending on the coil, check their specs for the resistance they ask for as there are many different available ratings.