Ballast resistor or no ballast resistor

[SMack]

Hey folks I’m sure this was covered at some point so I apologize up front.
On a new build I used a new Mopar electronic ignition system wiring harness and a Rev-N-Nator box , dist. , and coil. Can I bypass the ballast resistor or do I need it. Box is 5 pin by the way.
thanks folks

 

[JohnEngland]

You still need the ballast you rev n nator box is a 5 pin?

 

[SMack]

Can you elaborate a little John, with no points to protect what else does it do? I’m very electrical ignorant to be painfully honest

 

[dadsbee]

It's not there to protect the points... that's the condensers job. It's there to keep the coil from cooking.

 

[Kern Dog]

If you trust Rick Ehrenberg, the ballast resistor protects the ECU too.

 

[SMack]

Gotcha. Thanks guys as always much appreciated

 

[JohnEngland]

They covered it Pretty good ;)

 

[JohnEngland]

What are the volts at your coil with ignition turned to on, not running?

 

[RJRENTON]

If you trust Rick Ehrenberg, the ballast resistor protects the ECU too.

The ballast resistor LIMITS the amps to the coil, which in turn limits the amps the ECU's transistor switches....just MY opinion of course.....
BOB RENTON

 

[Jerry Hall]

Both 4 pin and 5 pin ECU's

 

[chrger1967]

I have a Pertronix II with a flame thrower coil. There is what looks to be a ballast resistor, but with the key on, I'm getting close to 12 volts in and out of the "resistor". Also, there is 12 volts at the coil with the key on. Do they make a ballast resistor for looks only?

 

[Unkle Krusty]

I chatted to the ignition builder and asked them, and the E shop. I have a Pertronix, and the resistor is not required. They also suggest a new coil, but I am still using the stock unit.

 

[chrger1967]

I chatted to the ignition builder and asked them, and the E shop. I have a Pertronix, and the resistor is not required. They also suggest a new coil, but I am still using the stock unit.

I'm just wondering why I'm getting 12 volts in and out of the resistor and 12 volts at the coil. Kinda makes me think it a dummy resistor.

 

[Jerry Hall]

When the ballast resistor isn't required a lot of times a solid wire is soldered into the ballast resistor.

 

[chrger1967]

When the ballast resistor isn't required a lot of times a solid wire is soldered into the ballast resistor.

The one that's on my car now, is a solid ceramic with now wires or anything in the back.

 

[Jerry Hall]

The one that's on my car now, is a solid ceramic with now wires or anything in the back.

Take a ohm meter with the ballast resistor unplugged and measure the actual resistance across the terminals. You will need an accurate volt/ohm meter. Depending on actual ignition the typical ballast resistor is .3-.5 ohms. That's not much resistance but should cause some drop in voltage. If it's 0, then it's for appearance only.

 

[Geoff 2]

^^^^^ This for checking the bal res resistance. NOT the method in post #11.

 

[451Mopar]

The ballast resistor is matched to the ignition coil to limit current.
The current limiting is mostly for when the ignition is on and the engine is not running, and running at low RPM.
With the engine running, Inductive Reactance will limit the coils current draw.

 

[HALIFAXHOPS]

You need one or the ecu will fry after a while. They also have to be matched to limit the current to the ecu.

 

[451Mopar]

On the stock ECU, the 5-pin module used the dual ballast resistor with the 5-Ohm section feeding into the fifth pin which connected to a Zener diode inside the box to create a voltage regulator for the ECU. The latter 4-pin ECUs just put the 5-Ohm power resistor inside the ECU. I don't know about the Rev-N-ator if it uses the fifth pin?
https://www.electronics-tutorials.ws/diode/diode_7.html