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Classic Truck Projects

Converting from 6 to 12 Volts
General Applications

FAQ on Converting

One of the most frequently ask questions we get are, "How do I upgrade to 12 volts". The 12 volt upgrade is probably the easiest and least expensive project. Before we get into the project, I would like to share a few of the most frequently asked questions.

Q: When I go to 12 Volts will I have to change my wiring or go with a larger size wire?

A: No, if your wiring is in good physical condition, there is no need to change wire sizes. Load amperage will drop by approximately 50% when changing from 6 to 12 volts.

Q: Will I have to change the starter to 12 Volt. ?

A: I most cases you will not have to change the starter. If a starting solenoid is used to engage the starter, it will need to be changed. If the starter is in poor condition with worn bushings and brushes, the upgrade to 12 volt may hasten it’s failure. In most cases it improves starting.

Q: I have a positive ground system, what do I need to do when changing to 12 volts?

A: Your best low buck option here is to run an inverter to keep the items you want positive grounded.


OK, lets get down to the project. As an overview to this project, we will cover the four basic areas needed to complete this project. These parts are the Charging System, Instrumentation System, Starting System and Lighting System.

Also See 1953-56 F-100 Wiring Diagram


The question of generator or alternator is one of, what is best for your needs. While 12 volt generators are used less often, a 12 volt generator makes it simple swap by changing out the 6 volt generator and voltage regulator. The amp meter will work fine on 12 volts, and give accurate readings. This would complete the Charging System phase of your project with no visible changes to the engine compartment. Another advantage of a generator over an alternator is that it will charge a dead flat battery.

A one wire alternator with built in regulator, which eliminates a lot of hardware, is easy to install as far as engine wiring goes. The old regulator and wiring can be removed, which cleans up the engine compartment. Usually, a bracket modification is required on most engines to fit an alternator. Aftermarket alternator brackets are available for most of the older 6 cylinder and V-8 engines. If you are even a little handy, you can modify the existing bracket to fit the new alternator by welding on a mounting boss.

To complete the Charging System you will need a 12 volt battery. Select one that meets your engine’s needs and battery box limitations. We recommend the new glass mat batteries by Optima. [more]