FORD TRACTOR 12 VOLT CONVERSION INFORMATION

NO, GOING 12 VOLTS DOES NOT MEAN YOU HAVE TO REPLACE EVERYTHING

We probably shouldn't use the word "conversion". It makes this electrical stuff seem way more complicated than it is. In fact the original 6 volt system works just fine as positive or negative ground. Many of these tractors have been changed to 12 volt, negative ground simply by installing a 12 volt battery with the negative terminal connected to ground, with NO OTHER CHANGES. The tractor will start and run just fine until the 12 volt battery is dead. One reason this works better than it should is the wire terminals probably have not been cleaned in ages, so most of the system never really sees anywhere near 12 volts. The 6 volt generator and regulator cannot charge a 12 volt battery. Many people who have done this just hook their 12 volt battery to an external 12 volt charger once in a while. If the tractor has lights, they may burn very bright for a short time. The 6 volt bulbs may seem to work ok just because ancient and dirty wiring and connections cannot deliver a full 12 volts to them. For the same reason the 6 volt coil may continue to work fine for a while. Just changing the battery to 12 volts is not a reliable conversion, no matter how many times it's been done.

One question often asked is how to prevent the starter from cranking backwards when the battery is changed from positive ground to negative ground. Some small DC motors do reverse direction when polarity is changed. The starter on these tractors is a series-wound motor. What that means is the starter will always run in the same direction regardless of polarity.

Some people ask if there are any differences in the wiring for headlights in a negative ground system vs a positive ground system. YES! If you wire the headlights wrong, they become light suckers and will try to suck all the light out of the room! Oops, sorry about that, I really should restrain myself. No, the bulbs won't turn into "black light" bulbs either. Standard headlight and taillight bulbs don't care about polarity. With the switch ON, current flows, and the lights glow. If you are changing any bulbs to LED type, polarity often does matter. If the LEDs are not reverse-current protected, hooking them up backwards will instantly burn them out. Better LEDs should be reverse-polarity protected. If they don't work, reverse the wires and they work.

In most cases conversions will use an alternator to charge the 12 volt battery. My recommendation is to get the 1-wire delco alternator, connect the one large generator charging wire to the alternator output, remove the voltage regulator, and small wires between the regulator and generator. This greatly simplifies the wiring and does away with several possible mistakes that can instantly fry the new alternator. Another option that requires zero wiring changes is to use a 12 volt generator and voltage regulator. The 12 volt versions can replace the 6 volt parts with no wiring changes. Many tractors just a few years newer used 12 volt generators and regulators that are almost a direct swap.

Once the 12 volt battery is being charged all the time, the next reliability issue is the ignition coil. My recommendation is to buy a 12 volt replacement coil. For the front mount distributor, the 12 volt replacement coil is designed to work with the original wiring and ignition resistor with no changes. It's a direct swap. For the side mount engine get a 12 volt round can coil that does not require an external resistor. The box may say something like internal resistor or no external resistor required. This 12 volt coil is also a direct swap with no wiring changes. If the two small round can coil terminals are marked the negative coil terminal goes to the distributor with a negative ground system.

STARTER SOLENOID PROBLEMS:

The 9N and 2N tractors use a mechanical start switch rather than a solenoid. The start pushbutton operates a pushrod that passes thru the steering column to the switch located on the front of the steering column, below the battery. That switch can melt down internally and fail. Adding spacers to make the pushrod longer might get it to work, but this is definitely a temporary solution.

That starter solenoid on the 8N tractors may look like a standard Ford automotive part, but it isn't. The tractor solenoid has the small terminal wired hot. That terminal connects to ground when the start button is pressed. I believe the tractor solenoid is only available as a 6 volt part. Don't worry about that. The 6 volt solenoid will work just fine at 12 volts. If you do buy a 12 volt solenoid, it probably won't work. There are at least 5 different starter solenoids that look identical or very similar to the Ford tractor solenoid. Looks can be deceiving. Some will have one small terminal. Others will have two small terminals. The way those terminals are connected internally varies depending on the application. For most (if not all) automotive applications, the small start terminal is looking for a switched hot wire from the start terminal on a standard automotive turn-to-crank engine ignition switch. None of them will work with the push-to-crank engine safety interlock pushbutton on these tractors.

The solenoid mounts to the top of the starter motor with the small terminal pointing towards the engine. Logically, it seems like it should mount so there will be easy access to connect the wire to the small terminal. Wrong. It will not work unless the small terminal is between the solenoid and engine block. My guess is that Ford engineers did it this way so brush and branches wouldn't tear that small wire loose.

CAUTION

One reason the word "conversion" causes many problems is the thousands of different rewiring schemes. Many of these conversions never work right. None can be easily understood by the next person trying to fix a problem. Custom wiring just sucks when there is a problem, even when it's my own custom wiring. Trying to remember what goes to what is a nightmare. Here's a link to my hall of shame photos titled "How NOT to Rewire Your Tractor":

Please, stay as close as you can to the original wiring, or simply buy a new wiring harness.

A new tractor wiring harness is CHEAP! It is probably one of the least expensive upgrades you can do for your vehicle. The low-end bargain main tractor harness will run you about $25. The high-end "Just Like Original" main harness may cost $50 or more. The low end harness will usually be put together with crimp-on connectors. The high-end harness should have soldered connectors protected with heat-shrink, so it is completely waterproof. Either harness will work much better than many of the "self-wired" jobs I have seen. The cheaper harness will obviously not last as long if it is exposed to weather.

No wiring changes are required to go from 6 volt positive ground to 12 volt negative ground if a 12 volt generator and regulator are used.

A 12 volt conversion using the Delco 1 wire alternator can still used most of the original 6 volt wiring.

NOTES FOR WIRING DIAGRAMS

All of my wiring diagrams show the light circuit connected directly from the battery. One reason is so the lights can be switched on with the ignition off. Leaving the ignition on when the engine is stopped can cook the coil. Another reason is to reduce the amount of current going through the ignition switch. Many people prefer that everything goes off when the ignition is turned off and connect the light switch to the switched side of the ignition switch.

The 12 volt conversion diagrams for a 3-wire alternator show a diode that can be soldered in-line and protected with a piece of heat-shrink. This diode allows use of the original 2-wire ignition switch and can be concealed in the wiring harness. My preference is to use a 3 to 5 watt incandescent bulb on the dash in place of the diode. The bulb provides an "ignition on" indicator light that I find to be very handy. Panel lights can be bought that snap into a 1/2" hole in the dash. As you can see from the diagrams, the best (simplest) conversions are to use a 12 volt generator and regulator or use a 1-wire alternator.

My diagrams for the 3 wire alternator show a connection for the alternator "voltage sense" No.2 terminal. There is already a pair of small generator wires in the 8N harness that go all the way to the dash, why not use them to properly connect the small terminals on your new 3-wire alternator? Most other conversions connect a short jumper directly to the BAT terminal on the alternator. It will work that way, but I believe in most cases, that short jumper is a waste of time. Many rebuilt Delco 10-SI alternators should revert to internal voltage sensing when the voltage sense terminal is disconnected, so jumpering the voltage sense terminal to the alternator output should not be required. "MOST" 10-SI alternators should revert to internal voltage sensing, and work with the No.2 terminal not used. However, there are more than a few different designs of the internal regulator used in these alternators, so there is absolutely no guarantee they will all work the same way. If you have left the voltage sense terminal empty, and the alternator does not charge, before doing anything else, connect a jumper from the No.2 terminal to the BAT terminal, and try it again. Make sure you are running the engine fast enough for the alternator to self-excite. Anything around half throttle should be enough.

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