ELECTRICAL

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

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 loose 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. The zinc plating will give itself up to protect plain steel studs, threads, etc. This process is called galvanic action. When different types of metals are in contact with each other and moisture is present, one metal will become sacrificial and protect the other. We want to make sure the one that becomes sacrificial is the least valuable and easiest to replace (the nut and washer).

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 make. There are a few cheap replacements with crimped ends, some better waterproof replacements, "Just Like Original" harnesses from somebody like Dennis Carpenter, or several restoration wiring suppliers. The price range for the main engine harness is generally from $25 to $80. You often get what you pay for. Most of the cheapest 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 harnesses are #12(ignition ckt), #10(light ckt), and #8(charging ckt). YES, the wire sizes mentioned here are one or two sizes larger than my diagrams show. Why? The diagrams show original wire sizes. The wires don't need to be any larger, but the original wire used on these tractors had rubber insulation. Rubber insulation was much thicker than modern thermoplastic insulation. By going up one or two sizes, I think my wiring LOOKS more original. Plus, the bigger wire is stronger, carries more current, and causes less voltage drop. I use the same sizes for 12 volt wiring for all the same reasons and someone may decide to switch back to 6 volts.

If you want to create your wiring from scratch, you should 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. I have seen a couple of good-looking wiring jobs using solid copper building wire! I do not recommend using solid core wire for any vehicle wiring. It can certainly be bent to follow precise paths. The additional vibration transmitted to switches, terminals, and bulbs by solid wire can't be good for long life of those components.

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, most of it was solid color with a contrasting stripe.

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

Written instructions with no theory or confusing diagrams

The tangled mess of wires on your tractor (or even 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 their 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 many of 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 three or four pieces of #10 or #8 AWG size wire that will usually have yellow colored insulation.

CHARGING CIRCUIT

1-The large screw terminal located on the end of the generator is the main generator output from the armature winding that charges the battery. It should have a large wire (Yellow with Black stripe) 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 (Yellow) that goes to one post of the terminal block. On the early, 3-post terminal blocks with a resistor, use the bottom terminal. On the 2-terminal type, without a resistor, pick either one.

3-From that same post on the terminal block, another large wire (Yellow) goes to the Ammeter.

4-From the other side of the ammeter there should be a large wire (Yellow) that connects to the same Solenoid terminal where the 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 visibly marked. It's usually stamped into the case, but may be very light, rusty, or painted over 6 times. Two small wires go from these terminals directly to the voltage regulator (VR). The ground terminal will be the one that is not insulated from the generator case. The ground wire (Black with Red stripe) 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 terminal is the generator FIELD. This wire (Black with White stripe) connects to the VR field terminal marked "FLD".

DONE!, and that was the hard circuit!

IGNITION CIRCUIT

6-Connect a small wire (red) from the coil to the terminal 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.

7-Then, to complete the circuit, you connect the two wires from your ignition switch to the terminal block. If you have the 3-post one wire goes to the bottom post and the other connects to the opposite side of the resistor. For the 2-post terminal block one wire goes to each post.

STARTING CIRCUIT

8-Last, the small starter wire (Red with Blue stripe) 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 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. It certainly saves wear and tear on 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 only a couple of extra wires to run, but I believe the improvement is worth it. Some people think I have 12 volt lights on my tractor!

DID YOU POLARIZE THE GENERATOR ?

WHAT? Yep, I immediately glazed over with a blank stare the first time someone asked, "did you polarize it". These 6-volt systems can be very wierd, even for someone who has worked on all sorts of vehicles for well over 30 years. I thought this might be another barnyard spoof or snipe hunt for the rookie tractor owner. Here we go again, or maybe the last batch from the still was a little too strong?

The 6-volt generator can get confused when it has been disconnected from the battery. The generator may "forget" which way it was wired. Really? I was not convinced until doing some on-line research for myself. Wow! he wasn't pulling my leg after all!

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.

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If you came here looking for 8 volt conversion info or regulator adjustment info. I've published what I have on the subject, HERE

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.