12 Volt Conversion
by John Milliman

Tired of Dim Headlights?

      Ever wanted to convert to 12 volts, but didn't want to sacrifice your original engine compartment? Well, here's a few tricks to help you solve your problem while staying original at the same time. Thanks to Patrick's Antique Cars and Trucks for information quoted from their catalog.

Wait! I have a positive-ground GMC, what do I do?

      This so easy, you'll kick yourself for not having figured it out on your own. All you have to do to convert that Jimmy to negative ground is:

1. Disconnect the battery (VERY important first step)
2. Reverse the wires on the coil
3. Reverse the wires on the ammeter
4. Reverse the battery cables. While you're at it, why not switch the ground cable from going to the frame to a starter mounting bolt or the transmission? It's better than the frame.
5. Put all your tools away and sweep the garage floor, because you are DONE. Oh, yeah. Power up the system to see if you did it right.

    Easy job. By the way, this method works for Fords, too (should you have one laying around).

12 volts, but looks all original

• Disconnect and remove the 6-volt battery. If you discard it, make sure you do so properly. Used Lead acid batteries are hazardous waste, so please dispose of them properly -- it's the law.
• Remove your 6-volt generator.
• Replace with a 12-volt generator. I got mine from a guy hotrodding a '57. It fit perfectly and looks almost identical to the original 6-volt unit.
• Remove the 6-volt voltage regulator and replace it with a 12-volt one. Again, you can probably use the one that came with the 12-volt generator you found.
• OR, if you want to be anal and maintain strict originality, you can use your 6-volt generator -- just take it to a good electrical shop and have them replace the 6-volt field coils with 12-volt ones. Just don't forget to replace your voltage regulator...
• Replace your 6-volt bulbs (headlights, taillights, parking lights, dash lights, dome lights, etc) with 12-volt bulbs.
• Put a ballast resistor* in the line between the ignition switch and the coil
• Put a voltage reducer* in the power line to each 6-volt accessory switch (radio, heater, etc)
• Put a Standard Ignition* in the line to the gas gauge.
• Install a 12-volt coil
• Install a 12-volt battery that fits your battery tray (duh).
• Power up the system and check it out.

12 volts, but with an alternator

• Disconnect and remove the 6-volt battery. If you discard it, make sure you do so properly. Used Lead acid batteries are hazardous waste, so please dispose of them properly -- it's the law.
• Remove your 6-volt generator, coil and voltage regulator.
• Install the alternator. You'll probably have to do some bracket modifications.
• Use a DA plug on your alternator (because most modern alternators have built in regulators, this eliminates the voltage regulator on the firewall)
• Take the "Batt" wire that used to go to the regulator and connect it to the red wire of the DA plug.
• Connect the white wire from the DA plug and connect it to an "ignition" spot, either the ignition switch or the coil wire.
• Wrap up the "field" and "arm" wires that used to connect to the regulator because you don't need them anymore.
• Replace your 6-volt bulbs (headlights, taillights, parking lights, dash lights, dome lights, etc) with 12-volt bulbs.
• Put a ballast resistor* in the line between the ignition switch and the coil
• Put a voltage reducer* in the power line to each 6-volt accessory switch (radio, heater, etc)
• Put a Standard Ignition* in the line to the gas gauge.
• Install a 12-volt coil
• Install a 12-volt battery that fits your battery tray (duh).
• Power up the system and check it out.

• Part# EL110 Voltage reducer (Light duty for gas gauge)
• Part# EL135 Voltage reducer (Heavy duty for accessories)
• Part# EL181 Voltage reducer (for ignition points)

      The part numbers may have changed since 1995 when I bought mine.

Alternator Installation

v. November 05