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Choosing a coil. Ballast vs. non-ballast? (1 reply)

6 years ago
LorraineLH 6 years ago

Choosing a coil. Ballast vs. non-ballast?

6 years ago
LorraineLH 6 years ago

This is an original tutorial from http://classicmini.weebly.com
Wiring diagrams courtesy of Advance Auto Wire

[b:3eqnaaq4][u:3eqnaaq4]Ballast vs. non-ballast[/u:3eqnaaq4][/b:3eqnaaq4]
One of the most confusing items I came across was the uncertainty of whether I had a ballast or a non-ballast coil and what that really meant. I think it's important to understand that these two coils are designed for different ignition systems. A ballasted system is designed so the coil's normal operating voltage is around 6-9 volts and a non-ballasted system is designed to operate around 12 volts. This may have nothing to do with the voltage in the rest of your car's charging system, so don't think that just because your battery outputs 12 volts, you have a non-ballasted coil. The type of ignition system determines the resistance of the coil you should be using. A non-ballasted coil should be 3 ohms and a ballasted coil should be 1.5 ohms.

[b:3eqnaaq4][u:3eqnaaq4]Why are there two?[/u:3eqnaaq4][/b:3eqnaaq4]
Ballasted ignition systems were designed to accommodate a wide range of operating conditions. A 3 ohm coil can only produce it's power when it is being supplied the necessary 12 volts. This means that in cold cranking situations when the batteries voltage dropped, the coil wasn't receiving enough power to create a spark.

On the flip side, there is the 1.5 ohm coil which is happy to operate in these lower voltage scenarios. Unfortuantely, they would burn out quickly if operated constantly at 12 volts. The solution to this problem was the ballast which reduces the voltage down to the 6-9 volts the 1.5 ohm coil prefers. It isn't, however, just that simple. In order to maximize the coil's output during starting, ballasted ignitions have a ballast bypass which sends 12 volts directly to the coil during startup. This doesn't create any issues for the ballast because the jump wire now creates 12 volts on both sides of the resistor. There is no longer a current flow, so the resistor doesn't do anything.

[b:3eqnaaq4][u:3eqnaaq4]Which one do I have?[/u:3eqnaaq4][/b:3eqnaaq4]
Determining which ignition system you have is quite simple. Connect a multimeter to the ignition side of your coil (usually the positive side) and ground, and then turn the ignition on. If you get a reading of between 6 and 9 volts, you have a ballasted system. If, on the other hand, you get a reading of around 12 volts, you have an non-ballasted system.

Once you recognize that there are only two systems and the coils are specific to those systems, the multitude of coil choices becomes a lot more manageable. Unless you want to change your system, you can immediately ignore half the coils. That then leaves you with only a couple more choices: stock coil or sports coil. This is really a choice that can be left up to you. Sports coils offer the ability to provide higher voltage to your spark plugs which creates more 'boom' in the cylinders. This extra explosiveness can translate to more power, better fuel economy (due to more completely combusted fuel) and a smoother running vehicle. If you do switch the a sports coil, you need to regap your spark plugs. If you fail to take that step, you will negate the benefits of the spark plug. The gap between the anode and the cathode has to be widened to allow the higher voltage to build before the electricity jumps the gap.

[u:3eqnaaq4][b:3eqnaaq4]I want a change[/b:3eqnaaq4][/u:3eqnaaq4]
Maybe you might want to switch because you are running an electronic distributor which needs 12 volts or you are trying to get the most out of your sport coil. Whatever the reason, the process to change from a ballasted system to a non-ballasted system seems fairly straight forward. It requires replacing your 1.5ohm coil (assuming you hadn't already installed the wrong coil) with a 3 ohm coil, and providing the 3 ohm coil with 12 volts.

If we compare a ballast system to a non-ballast system, we can see that there is a small difference in the wiring.
[attachment=1:3eqnaaq4]Non-ballast coil.jpg[/attachment:3eqnaaq4]
[attachment=0:3eqnaaq4]Ballast coil.jpg[/attachment:3eqnaaq4]
The top photo is a non-ballast coil. It's a fairly simple system where the positive side of the coil receives 12 volts from a switched source (only powered when the ignition is on). The negative side of the coil connects to the distributor and the tachometer.

In contrast, the ballasted ignition has an extra wire on the positive side. The first wire on the positive side comes from the switched source just like the non-ballast coil. The difference is the ballast is built into the wire to ensure the voltage is reduced from 12 volts by the time it reaches the coil. The second wire comes directly from the starter and jumps the ballast resistor. This wire is only powered when the starter is being run.

By comparing these two diagrams, you can see how easy it is to convert from a ballast to a non ballast. Just disconnect the wire coming from the starter and replace it with a 12 volt switched source. This would most likely come from the fuse panel. Even simpler would be to remove the wire from the starter and connect that to a switched 12v lead. Just make sure your new connection is only powered when the ignition is on. Apparently it's not necessary to disconnect the ballasted 12v wire. And that's all there is to it.

This is an original tutorial from http://classicmini.weebly.com
Wiring diagrams courtesy of Advance Auto Wire

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