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DISCLAIMER: Specifics are for a '64 Riviera. There are slight differences in the wiring between the Riviera and other full-size Buicks, and there may be differences between model years. Double check this information against the wiring diagram for your car before doing something you may regret, particularly with regard to wire colors and terminal numbers.

If you want to install a Pertronix system in your car, you should be aware that the voltage at the ignition coil is limited to ~ 9V while the car is running.  This is done to minimize the pitting that would normally occur at the points.  The voltage is lowered by running the current to the coil through a resistance wire that is in the circuit between the ignition switch and the coil.

The start and run circuits on a '64 Riviera are different. When the key is in the start position, the resistance wire is bypassed, which provides 12V to the coil/points. This is done via the yellow wire from the starter. If you trace it back to the firewall connector, you will notice that it connects to the pink wire that runs to the coil. This brings us to a common misconception: the pink wire is *not* resistance wire; it's just standard 16 gauge wire. The resistance wire runs from the ignition switch to the firewall connector inside the dash harness. In the wiring diagrams it is listed as W.O.P.C.T. (white with orange and purple cross tracer (res. wire 1.8 ohms.)).

When in the start position, the current to the coil runs from the battery to the ignition switch (red wire), to the starter (purple wire; via the neutral safety switch at the console shift lever), to the firewall connector (yellow wire), to the coil (pink wire). By bypassing the resistance wire, you get the full 12 V at the coil.

In the run position, the current to the coil runs from the battery to the ignition switch (red wire), to the firewall connector (resistance wire), to the coil (pink wire). Routing the current through the resistance wire knocks the coil voltage down to ~8.5 V.

Note that all of this may be moot. I called Pertronix about the installation in my '64 Riviera to ask about this, as I get 8.5 V at the coil with the engine running. I wanted to know if I had to run a new wire to get 12 V to the Pertronix module and/or coil. I was told that both will work at 7.5+ V. This means that even with the resistance wire in place, you should run just fine tapping off the coil terminal.

If you absolutely have to have 12 V at the coil/points before you can sleep at night, you have a couple of options:

  • You can either replace the resistance wire from the ignition switch to the firewall connector or run another wire in parallel. If you chose to run a second wire, it will effectively negate the resistance wire. The advantage of running a wire in parallel is that you can return to the stock set setup (in case you want to return to points) with a simple snip of the new wire. It's also cleaner; no one will ever see your modifications. The disadvantage of this idea is the pain in the butt factor. All of this work takes place under the dash (with you on your back), and requires you to pull your ignition switch and maybe the firewall connector so you can get to the appropriate terminals to make your connections. However, you can avoid pulling the switch and connector by using the wire taps described at the end. In this case, you would bypass the resistance wire by tapping it at both ends:
                resistance wire (in dash harness)
    firewall |--/\/\/\/\/\/\/\/\/--| ign switch
                    new wire
  • If you want to do this all under the hood, you can tap terminal 4 (brown wire) of the voltage regulator. It is hooked up to IGN terminal of the ignition switch, and, once the car is running, it draws 12V directly from the battery.

When tapping wires, I recommend using the quick-connect wire taps (e.g. Radio Shack part # 64-3052 (Tap-In Squeeze Connectors for 18 to 14-gauge wire)). They work by piercing the insulation, and require no stripping, soldering, or anything else; you simply squeeze them together.

*Special thanks to John Chapman for his contributions.

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