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john Mitchell

Burning Out a Pertronix Unit

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Quote Originally Posted by wittsend View Post
A lot of people think that because it is an "electronic" ignition, the Pertronix sends 12V positive to the coil - but that is incorrect. All the Pertronix does is electronically replicate what your points did, which is (temporarily) connect the coil to ground. Hence the coil should be used with whatever resistor it had originally. The coil resistor has (essentially) nothing to do with the Pertronix device itself.

Where people get into trouble is they will take the red, 12V positive wire for the Pertronix and connect it to the resistor-ed side of the power going to the coil. Then they will have less than 12 volts running the Pertronix. It is best to wire it directly to the ignition switch, and even better through a relay. I also recommend using a slip connector for the red, 12V wire to the Pertronix. That way when you need to have the ignition on in a sustained fashion, without the engine running, you can keep from frying the original version of the Pertronix by easily disconnecting it.

I agree with Mr. Vine's assessment of the original Pertronix design being poor. One idea I had was to design a 555 timer circuit so that if it did not see a pulsing of the signal (meaning engine running) it would shut down the Pertronix 12V+ power after... 20 seconds (they say the original Pertronix can fry in as short as 30 seconds). This of course is just one more thing that can go wrong. So, I'd put in a three way switch for timer based shut off, bypass (meaning 12V+ goes directly to the coil resistor, not through the timer) and a circuit break position (complete disconnect) to eliminate the need for disconnecting the red wire I mentioned above.
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