The Easy 12 Volt Conversion

All N-Series Tractors - Ford-Ferguson 9N, 2N, Ford 8N, and NAA

Tractor Wiring 101 For The Electrically Challenged.

This is condensed written conversion instructions with no confusing diagrams or electrical theory. Nobody really wants to know that "stuff" anyway, right? GRIN.

The tangled mess of wires on your tractor (or even the brand new harness you bought) may appear impossibly confusing, but the wiring on these old Ford tractors is really very simple. The following should walk you through a complete 12-volt rewiring job. All LEFT, RIGHT, FRONT, BACK directions are based on the operator sitting on the seat looking foreward.

Before you start messing around with the wiring, disconnect the ground lead at the battery. Better yet - Disconnect both battery cables, take the mattery out, and put it on a charger/maintainer. If you don't have an automatic 12 volt battery charger, get one.

I will assume your current wiring system is the typical complete hack job. Often you are dealing with a failed 12 volt conversion that maybe never worked.

I will assume you have already dealt with the physical issues of mounting a 1-wire alternator with the correct 2" pulley and the correct belt.

Take apart all wiring connections and remove the old wiring. Nuts and washers that look shiny can be twisted loosely back onto the studs. Collect rusty, or rounded hardware, take it to the hardware store, and buy new shiny, zinc-plated, hardware to replace it. Do not buy stainless steel, copper, or any other metal hardware. Most hardware stores have a place where you can match up threads and sizes, or someone who will do that for you.

LOOK at the surface around each post where the terminal goes. If the surface isn't shiny, make it shine. A small file will work, but don't mess up the threads. if you are re-using hardware. Lay the back side on the file and slide with your finger to shine them up.

Remove the voltage regulator and anything else that won't be used in the new system. Check all switches with an ohm meter or just replace them. They aren't that expensive.

Buy a new 12-volt wiring harness. You get what you pay for, but even a cheap harness is better than what you started with. Look at the harness. Each wire has two ends. They should be color-coded so you can find the two ends of each wire.

CHARGING CIRCUIT

Let's start with the most difficult system and work down from there. Starting with the battery charging circuit will also let us begin with the wires in the harness that are noticeably larger in size. There should be three or four lengths of large size wire that will usually have yellow colored insulation. Sometimes it's Red. Find the longest length of this large size wire at one end of the harness (usually Yellow with Black stripe). That will be the front end of the harness. There should be a smaller (usually Red) wire with it. Ignore the small wire for now. Some tractors have a wiring "tube" along the top of the engine. These two wires go through that tube.

Find the large screw terminal located on the back of the alternator. This is the main output that charges the battery. Connect the long wire we just found (usually Yellow with Black stripe) to this terminal with the nut and washer provided. Just hand-tight for now. Find the other end of that same wire. It goes directly to a terminal on your junction block on the back of the dash. Lay the harness out so this wire ends up on the left side behind the ammeter.

If you have a 9N, 2N, or early front distributor 8N, the junction block also has a resistor. Connect the other end of this alternator wire to the bottom post. Newer tractors don't have ignition resistors, the junction block is smaller, black, and only has two terminals. Connect the alternator wire to either terminal.

From that same post on the junction block, another very short large wire (usually Yellow) will connect. The other end of that wire goes to the Ammeter. Pick either ammeter post for now.

From the other post on the ammeter there should be another, slightly longer, large wire (usually Yellow) that connects to the large Solenoid terminal where the large battery cable connects. It will hve a larger ring terminal that fits the solenoid battery conection post. Some ammeters were "inductive type" and one piece of wire takes care of the previous two steps. The wire just passes through a loop on the back of the ammeter.

Charging circuit is DONE! That was the hard one!

IGNITION CIRCUIT

Go back to the front of the tractor. Connect the small wire (red) to the coil. The other end of that red wire will be back by the junction block. If you have the 3-post terminal block, pick one of the two terminals that connect to the resistor. On the 2-post block use the empty post that you didn't use before.

To complete the ignition circuit, you simply connect the two wires from your ignition switch to the junction block. If you have the 3-post type with a resistor, one wire goes to the bottom post and the other connects to the opposite side of the resistor from where you connected the red coil wire. For the 2-post terminal block one wire goes to each post.

Ignition Circuit is DONE! See how easy this is!

STARTING CIRCUIT

Find the small start wire (usually Red with Blue stripe) down by the start solenoid. This one goes straight from the small terminal on the Solenoid to the Start PushButton.

This 1-wire circuit may seem strange, because it is. The Tractor solenoid is totally different from the way most automotive start solenoids work. Most of the automotive solenoids do nothing until you apply voltage from a start switch to the small post. The START post on the tractor solenoid is HOT all the time. This terminal is grounded when you press the Start Switch to engage the starter.

No conversion will permanently fix all of the things that will cause an 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.