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These are just a few examples of other electrical system conversions for the Ford 8N Tractor electrical system. There are hundreds of conversions that half work or don't work at all. Some of these examples use the original or a rewound GENERATOR instead of an alternator. You give up performance since an alternator puts out a lot more current, especially at low RPM. But the generator looks more original, is weatherproof, and is a far more durable and forgiving part than the automotive alternators most often used.


An often overlooked upgrade that might be more appropriate for these tractors is an upgrade to 8 volts or even 12 volts using the original generator or one rewired for 12 volts. Both of these upgrades may be more appropriate for many show tractors or working restorations. You can leave the standard wiring exactly like original and the installation LOOKS original!

If you use either of these suggestions, please make sure the regulator, battery and generator are clearly labeled with the new voltage and correct polarity if you also changed that!

The most often neglected part of any conversion is DOCUMENTATION! Please keep a record of what you did, preferably labeled right on the tractor, so the next Owner (or you) won't have to pull all the wires off and start over. I see dozens of inquiries from people trying to troubleshoot conversions with no idea how their conversion was done.


The 6 Volt Negative Ground Conversion - This is not really a conversion. Many have bought a battery with the plus and minus terminals reversed, or simple stuck the battery in wrong way around. This mistake will instantly FRY most electrical systems that use an alternator. The original electrical system with a generator will work just fine as a negative ground system. If you have a round can coil with two small terminals, the grounded side of the coil goes to the distributor matching how the battery is connected. So, if the battery is connected negative ground, the negative post on the coil connects to the distributor. Of course, you do need to POLARIZE the generator after making a change like this to get it to charge.

8 Volts

The 8 Volt Generator Conversion - It is possible to simply install an 8 volt battery and readjust the voltage regulator, so the original generator will put out a little over 9 volts. This requires someone with the ability or willingness to tinker with the innards of the voltage regulator. In order to charge a battery the generator must put out slightly more voltage than the nominal voltage of the battery. This is similar to putting air in a tire, it takes extra pressure to push the air into the tire. Add too much pressure, and the tire will eventually explode. Voltage is basically electrical pressure. Too much voltage will overcharge the battery, and yes, in extreme cases, the battery could explode.

ADJUSTING THE REGULATOR isn't difficult. Instructions for the adjustments were often included with 8 volt batteries.

The most important adjustment ia the charging voltage. The 6 volt generator output should be approximately 7.8 Volts. Anything over 9 volts will work for an 8 volt battery. Disconnect one battery cable, then carefully remove the Voltage Regulator cover. You should see 2 coils in the regulator. The voltage coil will have just a few turns of wire around it. and the contacts will be closed. Some regulators will have adjusting screws some don't. Turn the screw or bend the little metal tab to increase spring tension on the contacts. Increasing tension, increases voltage. Reconnect the battery, start the engine and check voltage with the engine running about half throttle. If there is no generator output, shut engine off, polarize the generator, and try it again.
When the contacts are closed the field coil in the generator is grounded so the generator output will be at maximum. As the voltage rises to about 7.8 to 7.8 volts the contacts will start to open and will vibrate between open and closed as it controls the charging rate to maintain the required voltage.

The second adjustmet is often skipped. This is the cutout adjustment on the relay that has normally-open contacts. For six volts this relay should close when the voltage increases to about 6.8 to 7 volts. It should open when the voltage drops to about 6.8 to 6.4 volts. For an 8 volt system, these settings should be increased about 2.1 volts.
Adjustment for the cutout relay most likely is a screw with a flat spring resting on it's head. Turning the screw counter clockwise will increase the pressure on the spring which will raise the voltage required to close the relay. Adjustment on the voltage regulating relay may be a screw but more common today is just a little arm that has the coil spring attached to it. If it has the arm, adjustment is made by bending it. Increasing the spring pressure will raise the voltage setting.

The 6 volt light bulbs will be brighter and probably won't last as long. On a front-mount you should add some additional resistance in the ignition circuit to protect the coil. Please refer to my comments on the Main 12 Volt Page regarding coils and ignition resistance.

The 12 Volt Generator Conversion - For this one you need to find a shop that will re-wind your generator to put out 14 volts. Then you can use a standard, off-the-shelf 12 volt regulator, 12 volt coil, and 12 volt bulbs.

Positive Ground Alternators - YES, it is possible to convert a normal negative ground alternator to work in a positive ground system. These have been created in both 6 and 12 volt versions. There's probably even an 8-volt version if you look hard enough. My question is WHY would anyone want to complicate life to this drgree? Most people see an alternator and immediately assume it's supposed to be negative ground. By using one of these, it virtually guarantees that the alternator is going to get hooked up wrong at some point and instantly fried.

I guess the lesson here is to just keep it simple and document whatever you decide to do. When I run into one of the oddball systems, it's because the system failed or never worked. My first recommendation is to put the original 6 volt system back on the tractor. If that's a NO, then go with the main stream 12 volt conversion.

No conversion will permanently fix any of the things that will eventually cause any electrical system to fail. The simple fact remains that these tractors do require more frequent maintenance than modern equipment. Open connections and unsealed switches are attacked by the environment and deteriorate over time. If you don't take things apart and clean the connections eventually they will fail. Changing the voltage may increase the time between maintenance but also increases the potential damage that can be caused. More voltage equals more energy to dissipate. Things that just looked dirty at 6 volts are often melted and useless when they fail at 12 volts.

Back to Main 12 Volt Page


Content and Web Design by K. LaRue — This Site Was Last Updated 31 MAR 2017.

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