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Old 09-22-2011, 08:46 PM
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ndutton ndutton is offline
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Here is Pertronix's discussion on input voltage, primary resistance and acceptable levels:

What type of coil can I use with the Ignitor™? How do I check my coils resistance? (12V negative ground only)

To determine if your system's coil is compatible with the Ignitor, some measurements should be taken prior to installation of the Ignitor. Caution… While performing this test, never leave the ignition switch on for more than 30 seconds at a time.

Set your voltmeter to a 15 or 20-volt scale. Attach an 18 or 20 AWG jumper wire from the negative coil terminal to an engine ground. Attach positive (red) lead of your voltmeter to the positive side of the coil, and the negative (black) lead to an engine ground. Turn the ignition switch to the run position. Now read the voltage at the positive coil terminal. Turn the ignition switch off. If the voltage measured is approximately 12 volts, no resistance wire is present. A typical resistance wire will provide 9 - 6 volts.

The next step is to determine the resistance in the primary ignition. Label the wires attached to the coil terminals and note their appropriate location. Make sure that the ignition switch is off and disconnect all wires from the coil. Adjust your meter to the lowest ohm scale. If you are using an analog style meter make sure to zero the needle.

Measure from the negative terminal to the positive terminal. Write your measurement down.

Now the maximum system amperage can be determined, divide your voltage measurement by your coil resistance measurement. This will give you the system current or amperage.

Four and six cylinder engines should not exceed 4 amps.
Eight cylinder engines should not exceed 8 amps. If the total amperage in your system is higher than the amount recommended for your application, you should install a ballast resistor.
If you have 14.2 volts at the coil terminal and a 3 ohm internal resistance coil, your amperage is 4.73, that's too much according to Pertronix.

My view on this is to avoid tweaking down the voltage regulator because of the negative resultant effect on battery charging. I believe a ballast resistor is the preferred method to maintain the 4 amp maximum and maybe a little less, remember 4 amps is a maximum.
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others

Last edited by ndutton; 09-22-2011 at 08:58 PM.
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