Ballast resistor - is this a must ?

[Stephan427SC]

hi guys,
is a ballast resistor in the positive wire of the coil a absolutly must ? When do I need it and why ?
thanks, Stephan

[Jerry Clayton]

for points type ignition --reduces the current/arcing across the contacts--is bypassed by starter relay for starting

[DanEC]

You need to tell us what type of distributor you are running and if you have a CD or transistor box to power it - or just points. Points need a ballast resistor.

[RadAirAndy]

Same as above!

[289ERAkit]

When you turn on the ignition key...you bypass the ballast resistor and the full 12v goes to the coil and points to provide a powerful start. When the key goes to the run position.... voltage goes thru the ballast resistor and voltage drops to 6volts (something less than 12v). If you can start your car and then it dies when your ignition switch drops to the run position....then your ballast resistor is open. Then you are stuck.... well...maybe not... get a wire and short across the ballast resistor.....your car will run with the full 12v but your points will take a beating after a while. Also....when you turn off the car remove that make shift wire... if you do not....I believe it will pop your coil.

MSD systems.... remove the ballast resistor and connect those two wires together. MSD wants the full 12v...all the time. (ERA type harness)

I learned this trick 30 years ago at Weirs Beach at 2 AM during Laconia bike week.... There were two helpful Canadian bikers who happened to be parked in front of me(by the bridge at the base of the hill). Not sure where I slept that night....

[mr0077]

Before electronic ignitions, during starting, the voltage available to the coil dropped to about 9 volts. To get a full spark, the coil was designed to operate at the current flowing during 9 volts, but after the engine started the voltage would return to 12+ volts and the current through the coil and points would increase. The ballast resistor was put in the circuit so that during starting the resistor was bypassed and coil would see 9 volts (and its related amps), then when the engine was running, the resistor would drop the 12+ volts back to 9 volts, and the coil was seeing the voltage and current for which it was designed. Because the coil was designed for 9 volts (and its related current), the points were too. If you take the resistor out (on an old system), the coil and points will see 9 volts and an appropriate amperage during starting and 12+ and a higher current when running. The excess current driven by the higher voltage will burn the points, and will probably cause eventual failure of the coil too.

On new (electronic) systems, the resistor is usually not necessary or actually must be deleted. Some new systems use points for a trigger, but they carry a very small current, which is the part that burns the points, so the resistor isn't needed.

Did I say that right?

[Stephan427SC]

I use the MSD 85805 distributor and a MSD 6AL. So if I understand right, I will need no balast resistor....?

[FWB]

Originally Posted by Stephan427SC

I use the MSD 85805 distributor and a MSD 6AL. So if I understand right, I will need no balast resistor....?

Correct. just go to MSD's web site and look at the PDF for install. it shows the wiring without a Ballast or resistance wire