ELECTRICAL

First, regardless if your tractor is 6 or 12 volts, you should carefully inspect the wiring. Look for cracked insulation, splices, bare spots, cuts, etc. What you are looking for on terminals is rusty hardware and any other signs of corrosion. You will usually find at least a few things that require attention. But, before you start mucking around with the wiring, disconnect the ground lead at the battery.

If there is any visible corrosion on any connection take it apart for cleaning. A small file works good for wire terminals and the base around terminal lugs. Rather than cleaning rusty hardware, it is much better to replace the nuts and washers with new zinc-plated hardware. When the plating is gone, the connections start to rust. This indicates it is time for new hardware with a fresh zinc plating. Please, do not use stainless steel hardware or copper washers! It might seem like a good idea until you find out that stainless steel and copper will cause any plain steel they touch to corrode much faster than normal! Zinc plated hardware is much better in this case since the zinc will give itself up to protect plain steel studs, threads, etc.

All switches should be checked with a decent ohm meter to make sure they are in good condition. There are only three, Ignition, Lights, and the Start Button. These switches have typically spent years out in all sorts of weather and can frequently cause mysterious electrical problems. If there is any question or you find any resistance across a closed switch with your ohm meter, replace it.

If your wiring harness is in bad shape, a new harness is easy to buy or even make. There are a few really cheap ($20) replacements but I would buy one of the better "Just Like Original" harnesses from somebody like Dennis Carpenter or build a waterproof harness myself. Most of the really cheap wiring harnesses are not even waterproof! See my section under "BUYER BEWARE" HERE..

For some odd reason American Wire Guage sizes are basackwards so the smaller numbers indicate larger wire sizes. The sizes I use for 6 volt wiring are #12(ignition ckt), #10(light ckt), and #8(charging ckt). Again, if you are replacing most of your wiring, I strongly suggest buying one of the better wiring harnesses with the proper terminals and rubber boots. The better ones cost around $80 but you can get cheap versions of the main wiring harness for as little as $15. The cheap ones are not made as well and will not last as long (your decision). If you want a harness that is "Exactly Like The Original" the simplest thing to do is to buy one of those from Dennis Carpenter.

If you still want to create your wiring from scratch be sure you use automotive grade stranded primary wire. The individual strands are much finer than stranded building wire so it is more flexible and less likely to break. Try to stay as close to the original color coding as possible. The trouble here is that the original wiring was not plain solid color insulation, it was solid color with a contrasting stripe.

Like the fabric covering, the original color wire can be bought from antique restoration suppliers for a premium cost. (There, that was for the originality police). My method of dealing with the contracting stripe wire is to buy the correct solid colors of wire and then use colored heat-shrink tubing that corresponds to the stripe to insulate the ends. So a "red with blue stripe" original wire would become "red with blue ends" in one of my harnesses. I do not "RESTORE" old tractors, my mission is to keep old tractors working reliably while spending as little money as possible.

HOW TO WIRE A 6 VOLT FORD 8N TRACTOR

The tangled mess of wires on your tractor or even in the brand new harness you bought may appear impossibly confusing. But the wiring on a Ford 8N tractor is really very simple. The following section should walk you through a complete rewiring job.

How do I even begin to try and figure out this impossibly tangled mess of wires?

The easiest way I have found to help people get the wiring figured out is to break it down into separate circuits and deal with them individually.

This walk-thru is based on the original 8N tractor 6 volt wiring. Some earlier 9N and 2N tractors had one-wire generators and used a cutout instead of a voltage regulator. But many of those were later converted to the 8N type generator and voltage regulator, so this walk-through will work for those also.

Divide and Conquer

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 four pieces of #10 or even #8 AWG size wire.

CHARGING CIRCUIT

1-The large screw terminal located on the end of the generator is the generator output from the armature winding that charges the battery. It should have a large wire that goes directly to the terminal on your voltage regulator marked "ARM" or "GEN".

2-There should be a terminal on the regulator marked "BAT". This should also have a large wire that goes to one post of the terminal block.

3-From that same post on the terminal block, there should be another large wire that goes to the Ammeter.

4-From the other side of the ammeter there should be a large wire that connects to the same Solenoid terminal where the really large battery negative cable connects. 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.

5-The two small screw terminals on side of the generator are for "Ground" and "Field". They may not be marked, but they both go directly to the voltage regulator (VR), and the ground terminal will be the one that is not insulated from the generator case. The ground wire connects to the ground terminal on the VR marked "GND". If there is no GND terminal at the VR, just attach under one of the VR mounting bolts. The other wire connects to the VR field terminal marked "FLD".

IGNITION CIRCUIT

6-Connect a wire from the coil to the empty post on the terminal block.

7-Then, to complete the circuit, you simply connect the two wires from your ignition switch with one to each of the two posts on the terminal block. There is no right or wrong way, either switch wire goes to these terminals, and the switch just opens or closes the circuit (ON-OFF).

STARTING CIRCUIT

8-Last, the starter wire just 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.

If you do have lights, these will be the longest wires on your tractor, and they carry the most load, so voltage drop is a concern. I run #10 AWG wires for 6_volt lights so they will be as bright as possible. I wire the light switch hot, ahead of the ignition switch, so I can turn the lights on with the key switch off. This is a convenience that might also save the coil and less current has to flow through the ignition switch.

Another wiring improvement is to run two wires to each light. One wire connects to the light switch for power, the other brings the ground all the way back so you can ground it to the same point the main battery ground cable connects to the frame. This is a few extra wires to run, but I believe the improvement is worth it. Most people think I have 12 volt headlights on my tractor!

POLARIZING THE GENERATOR

When you are finished with the wiring, make sure the ignition switch is OFF and both battery cables are connected and ready to go.

Before you turn the key on or do anything else, you need to polarize the generator. You can use a jumper wire or just a flat blade screwdriver to momentarily short between the "BAT" and "GEN" terminals on the regulator. Sometimes they will be marked "BAT" and "ARM". You should get a spark. Done.

The polarization mentioned here should be done every time you disconnect the wiring to your battery, generator, or voltage regulator. Often the generator will maintain correct polarity without doing this step, but it only takes a second to make sure.