is a ballast resistor needed in a 240 with a 280 electronic ignition

[72zcar]

I have a 240z with a 280z electronic ignition distributor. I have been reading and it seems to say the resistor mounted on the fender well by the coil is not needed when you run a electronic distributor. And even limits the output of the coil because the ballast resistor was there originally to limit the voltage as to not fry the points, but since I have no points anymore taking the resistor out will increase the voltage output of the coil. Is this true? And if so do I simply remove the resistor and connect the wires together? Thanks...Bob

This is what I read:

BALLAST RESISTORS

Surprisingly, stock coils on older 12V points systems on every car were designed to operate with a max of 6-8 volts.

The reason is that on points distributors the entire voltage from the coil passes through the points, and too much voltage can burn them out.

So the ballast resistor was put inline with the 12+ wire to the coil to limit the voltage it puts out.

When you turn the key to start, the ballast is bypassed, and the coil gets a full 12V to put out a hotter spark for starting. Releasing the key inserts the resistor back into the circuit to preserve the life of the points. Why not design the ignition to use 12V all the time? Well, nowdays they do, but before 1977 or so that's the way all ignitions were designed.

This means if you buy a high performance coil and simply install it, the ballast resistor will usually limit the new coil's power output to nearly stock. So on a points distributor If you connect a wire across the ballast, it will route a full 12-14v to the coil and pick up some voltage, but it can cause the points to burn out more quickly.

Don't bypass the ballast if you have a '75-78 280Z. The 280 brain supplies the coil voltage, and removing the ballast can hurt it by making the FI brain supply too much current. 280ZXs supply a full 12v and don't use a ballast resistor.

[hmsports]

I know with the Crane electronic ignition I put on my 240, they said that if the coil gets really hot within 10 minutes of running, it needs a resistor. I would have to look at the directions again but there were some installations that needed it and some that didn't and some that had it but used a 14 gauge wire jumper. I will look at the sheet again tonight and post some more info if you don't have an answer by then.

[EScanlon]

DITCH the resistor!

The 240 does not have a computer nor a bunch of complicated wiring to muck up the old basic wiring system. By adding the electronic distributor, the resistor is only working to heat up the air.

Disconnect it and you should be able to hook the wires together just as it says in the article you quoted.

That's the way it is on mine.

Enjoy the ride

[Dave Sommers]

Actually, both previous replies have merit to them.

The ballast resistor's job is to keep from cooking the coil, not the points. The voltage crossing the points is only to trigger the coil to discharge. High tension coil voltage only runs down the wires through the dist cap and rotor.

If you choose to bypass the BR you do need to check the temperature of the coil. A stock datsun coil will run too hot and burn itself right out in an amazingly short period of time. Aftermarket HP coils will probably run ok - unless they were designed to run at the lower voltage supplied by a BR.

Simple solution - get an MSD and problem solved, plenty of spark for any engine stock or modified.

[PetesPonies]

I am going to have to disagree with the last post. A ballast resistor is in an ignition system to drop voltage to the 8V range, we know that. When used in a points type ignition system, it IS there to allow the points to last longer. Increased voltage allows the current to arc across the points easier. The job of the condenser is to capture that electricl potential, allowin the primary ignition system to immediately collapse, and then inject this potential back into the system upon the next ignition cycle. The points would have a shorter life it operated at the full 12V. The coil can be designed to have 12V easily. They do it all the time in newer systems as well as racing. Now, many electronic ignition systems still used a resistance to cut primary voltage. This wasn't to protect the points, as there were none. However, the ignition switching circuit which replaced the points, can become overheated. So, can you go without the resistor? In this instance, I have no actual experince to give you. I do most of my work on Mustangs and the 240Z is newer to me. Many times an electronic ignition system used a resistance wire to cut voltage, so not seeing a ballast resister is not the total answer. I have run into this on Mustangs. Many MUstangers have used the factory electronic ignitions without a ballast and have fried the box. This does not mean the Datsun will be exactly the same, but something to consider. An electrical diagram will help. You can look for a resistance wire feeding the primary ignition system. Hope this helped.

[EScanlon]

First off: the 240 does not have an electronic "brain" / "box" / computer / or other components within the ORIGINAL circuitry.

Now, if you've completely changed the wiring, etc to include those components then you are no longer dealing with a 240 wiring, and must deal with your car accordingly.

Read the following articles found at these URL's:

http://www.mame.mu.oz.au/salman/zignitio.html

http://www.zhome.com/ZCMnL/TechPosts.html

http://www.zhome.com/ZCMnL/tech/ZXPertronix.htm

These are but a few of them. You will note that unless you are dealing with a Pertronix or MSD, they all point out that the ballast goes. Now this information is SPECIFIC to the 240Z. NOT the 260 or the 280, nor any other vehicle.

All I can tell you is this. The modification has been done on my car. My mechanic has over 25 years of experience working EXCLUSIVELY with Datsun / Nissan. He's checked and approved all the connections in the engine bay. If you want, I'll give you his name and you can set up an appointment for your car.

But enough, that's just my 2¢

[mattspod]

what about a 1980 280zx with matchbox igniter in a 76 280z? reoving the ballast and the transistor ignition module