Ballast resistor & Duraspark Ign

[Bronco919]

Do I still need the ballast resistor now that I have done the duraspark conversion? From my understanding the resistor was required b/c points couldn't handle the increased voltage from an aftermarket igntion.

Thanks!

Sam

 

[70_Steve]

All the wiring diagrams I've seen, including ones for upgrading to Duraspark and the Ford wiring diagrams for the 75-77 Broncos, all show a ballast resistor in series with the wire to the coil. Ford diagram says 1.05 to 1.15 ohms. I left the resistor wire in place when I upgraded my 70 to Duraspark, and it runs great.

 

[broncnaz]

I'm with 70_steve if you have stock wiring it will be fine although if its a add on resister than you may need to remove it unless it was added on because the stock resistance wire burned out then leave it. I did the duraspark swap on my 73 about 8 years ago still works great.

 

[Nobody]

As I understand, duraspark I requires the resistor, but duraspark II can be used without.

 

[RangerRob]

Pretty sure you want a full 12v going to the Duraspark module and a lower voltage (through ballast resistor) going to the coil. Unless you have upgraded your coil to one that doesn't require a resistor. In the older setups, the coil and the points needed the reduced voltage.

Check out
http://users3.ev1.net/~bmarr/duraspark_ignition_upgrade.htm

Good Luck!!!

 

[Bronco919]

I still currently have the resistor on there, and it does run just fine. I've just run across several mentionings like this:

Inductive-discharge ignitions date back to the earliest points-type ignition systems. In its simplest form, this system uses a set of points to trigger a coil. All coils operate on the same basic principal with a small number of primary windings outside a large number of secondary windings wrapped around a metal core. The positive side of the coil is connected to battery power while the negative side is connected to the distributor points and eventually to ground. The high-tension tower lead directs the output of the coil to the distributor and eventually to the spark plugs. Since points cannot handle a full 12-14 volts, a ballast resistor is used to reduce operating voltage to 6-8 volts and to limit the amount of current passing through the points.

What years did the Duraspark II run? I think I have the II. I hope. ;D

 

[76Broncofromhell]

I used a blaster II coil and just wired in a relay rather than deal with running a new wire. I hooked the ballast wire to the switch side of the relay and ran the source from the battery. I noticed it ran a little bit better in situations where the engine was loaded up.