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Unilite Conversion Wiring

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Old Jan 2, 2009 | 08:02 PM
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Default Unilite Conversion Wiring

I installed a Mallory Unilite conversion on my 73 today. I could hardly here the local AM radio station due to some RFI that I believed was from the distributor. The radio noise was greatly reduced.

Now for the question. In the instructions it says the power supply should be from the ignition and be less than 12 volts. The igniton switch wire to the coil is the resistor type with around 7 volts. Also attached to this wire is a regular wire coming from the starter solenoid. I believe this wire has 12 volts on it when the starter is turning and 0 volts when the starter is off. Seems like GM needed a higher voltage to the coil for starting. Does this wire from the starter solenoid need to be removed from the positve coil terminal so that 12 volts will not reach the unilite sensor? If so should it be disconnected at the starter solenoid?

Roger
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Old Jan 2, 2009 | 08:32 PM
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Originally Posted by RMS73
I installed a Mallory Unilite conversion on my 73 today. I could hardly here the local AM radio station due to some RFI that I believed was from the distributor. The radio noise was greatly reduced.

Now for the question. In the instructions it says the power supply should be from the ignition and be less than 12 volts. The person writing the instruction sheet was most probably a moron. The system voltage of your car is always 12 volts nominal. The igniton switch wire to the coil is the resistor type with around 7 volts. A resistor does not regulate voltage. It limits current. Also attached to this wire is a regular wire coming from the starter solenoid. I believe this wire has 12 volts on it when the starter is turning and 0 volts when the starter is off. The starter wire voltage is battery voltage, usually less than twelve volts due to the current draw out of the battery during cranking. Seems like GM needed a higher voltage to the coil for starting. The voltage is always 12 volts nominal, it does not change or increase. The resistor is bypassed during cranking in an effort to make the coil current somewhat equal (despite a lower battery voltage) to the current during normal run mode. Does this wire from the starter solenoid need to be removed from the positve coil terminal so that 12 volts will not reach the unilite sensor? If so should it be disconnected at the starter solenoid?

Roger
Probably not. During cranking, as I mentioned above, the system voltage (battery voltage) drops down a few volts. Bypassing the resistor during cranking will help restore the necessary primary current needed to fire the plugs. Worst case, you do not want to have a low battery condition from long cranking (cold weather or flooded carb condition), and not be able to get rid of (bypass) the ballast resistor. The starter shunt circuit compensates for low battery conditions, it does not magically create 12 volts at the coil.
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Old Jan 2, 2009 | 08:46 PM
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Roger..I think in your wiring instructions the wire labeled all other wires to the coil is the wire providing a full 12 volts during starting. You will notice that it says you need a reduced voltage for prolonged use.The 12 volts during starting is temporary and will not hurt the coil. It gives you a little extra spark during starting and then shuts off. It will only hurt your coil if it's on all the time.
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