[MikeK]

Originally Posted by Chuck Sea/Tac

What if you don't have points?

You need to make sure your transistor ignition module is capable of (1) switching the peak amperage and (2) dissipating the resultant heat generated by the semiconductor voltage drop. The killer of ignition modules is generally #2. That heat is a function of the dwell times the number of cylinders divided by 360 then multiplied by the heat (watts) calculated by the amperage times the semiconductor voltage drop.

Doubling #1, the switching amperage, easily done by simply going from a 3 ohm to a 1.5 ohm coil, will instantly double the heat. That is why pertronix ignitor modules are NOT recommended for use with low ohm coils. They will fail, usually somewhere inconvenient, like on an elevated interstate cloverleaf with no shoulders.

A standard pertronix ignitor module (the black ones) will burn up in less than 20 minutes if you leave the key on with the switching closed (reluctor not rotating, equivalent to points closed) with a 1.5 ohm coil. You have effectively driven the dwell to max and the heat builds faster than it can dissipate.

If you want any sense of reliability with the 1.5 ohm coil use the ignitor II (red color, 12V only!) module.