Ballast resistor question

limey66 · Oct 30, 2004

I have a Crane Cams PS20 coil ready to go in my 289 c code '66. I'm also installing a Crane XR-i electronic ignition module at the same time. My question is this:

How do I tell if a coil has an internal ballast resistance?

The Crane XR-i instructions say if I measure the resistance between the '+' and '-' terminals of the coil and it is between 3 and 4 Ohms it's got an internal ballast resistance. It has a 4 ohm resistance, BUT in the box with the coil is a nice ceramic resistor that has a 9 Ohm resistance - why would I need that? The Ford wiring diagram says that the ballast resistance in the harness is 1.3-1.4 Ohms, so 9 Ohms is overkill.

Help.

66HertzClone · Oct 30, 2004

Mustangs did not have a resistor built in the coil, they have resistance wire. It is usually covered with a woven fabric and is located under the dash. You can verify this by checking the voltage at the positive side of the coil.

limey66 · Oct 30, 2004

Ah, yes, but mine has been pulled about and came to me part re-wired with no ballast resistor or coil. I got the Crane coil but I don't know if it has a built-in resistance.

Thanks though.

Red Barchetta · Oct 31, 2004

limey66 said:
I have a Crane Cams PS20 coil ready to go in my 289 c code '66. I'm also installing a Crane XR-i electronic ignition module at the same time. My question is this:

How do I tell if a coil has an internal ballast resistance?

The Crane XR-i instructions say if I measure the resistance between the '+' and '-' terminals of the coil and it is between 3 and 4 Ohms it's got an internal ballast resistance. It has a 4 ohm resistance, BUT in the box with the coil is a nice ceramic resistor that has a 9 Ohm resistance - why would I need that? The Ford wiring diagram says that the ballast resistance in the harness is 1.3-1.4 Ohms, so 9 Ohms is overkill.

Help.

The only thing I'd double check is to see if that resistor says 9 or .9. Is there a part number on the resistor? Maybe then you could look it up to get the correct value as you're right, 9 ohms is overkill. Or, you could always give Crane a call, they should have the answer.

TOM B · Oct 31, 2004

A resistance wire or a ballast is ONLY used in a point distributor. so if you changed to a aftermarket or OEM electronic type distributor use full voltage only or you will not get the full (hot spark)

whwright · Oct 31, 2004

Some electronic distributors require a ballast resistor, most don't. Sometimes a distributor will require a ballast resistor with certain coils, but not with other coils.

Bottom line: follow the directions.

Wayne.

limey66 · Nov 1, 2004

Thanks guys.

Mopping up the various points above; I measured the additional supplied resistor as it has no markings on it at all, and that measures 9 Ohms, the car doesn't run so I can't check the voltage , the Crane XR-i kit is supposed to run with the factory ballast resistor or a ballasted coil - I don't know what I got...

In a nutshell, does a 4 Ohm coil sound like it has an internal ballast?

rbohm · Nov 1, 2004

i think if you check the instructions that come with the coil, you will find that crane says you have to use the ballast resistor that comes with the coil, EVEN IF you have a factory ballast resistor, or resistance wire. use the ballast resistor.

Ballast resistor question

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