FORD TRACTOR WIRE SIZE INFORMATION

Some of the original harnesses used an inductive ammeter where wire No.7 passed through the loop on the back on the ammeter. Most of the inductive ammeters have been replaced with the type having two screw-terminals. In that case, wire No.7 is cut and each new end is terminated on the ammeter posts.

Where two colors are indicated the second color is the small stripe on the original wire. I use colored heat shrink on the ends instead of looking all over and paying extra for the striped wire. A YelBlk wire in my harness will be Yellow wire with Black heat shrink on the ends. Where there was no stripe, my heat shrink matches the wire color. if you want the original striped wire, boots, and jacket material, these are all available from specialty shops that sell these types of "original" materials to restoration shops.

Materials Needed for 6 or 12-Volt harness:
Automotive Wire—Blk #12 Red #12 Yel #10
HeatShrink—Red Blu Blk Wht Grn Yel
Electrical Tape, Rosin Core Solder, Jacket material, Clips or Tie-Wraps.

Wire sizes can be smaller in a 12-volt system and modern insulation is thinner. There is nothing wrong with using the next smaller (larger number) wire guage than shown for the original 6 volt system. However, I choose to use the larger (smaller number) wire sizes indicated in the "My Size" column above for both 6 and 12-volt systems. Larger wire is more durable and looks more like the original wiring. I simplify things a bit, using the same size for all of the smaller sizes so there are fewer sizes and colors to buy. The ignition switch wires stay the same size because the switches I buy have the leads already on them. No, I'm not going to cut and splice them to go up in size.

Comparing the 6-volt and 12-volt diagrams should illustrate any changes.

ALTERNATOR CONNECTIONS

There are four connections on the 3-wire Delco 10SI, internally-regulated alternator. The connections are the large output terminal (BAT+), the ground terminal (GRD-), and two connections usually labeled 1 and 2. Terminal #1 is the "exciter" or "field" wire. Terminal #2 is the "remote voltage sensing wire".

There should be no confusion regarding the BAT+ connection. This large insulated threaded terminal post is the one that provides all the current for your accessories and to charge the battery.

The GRD- connector is another large threaded terminal post, but this one is un-insulated. This terminal is usually not needed unless the alternator is mounted to the engine with insulated brackets. It is possible for a paint or powder coat to act as insulation and prevent the alternator from being grounded. Scrape to bare metal where brackets and hardware mate, or run a ground wire.

Terminal #1

Most successful 8N Tractor conversions connect the field wire from this terminal directly to the switched side of the ignition key using an in-line resistor, bulb, or diode. If you use a diode, make sure you connect it the right way so it allows current to flow towards the alternator.

Terminal #2

Most conversions simply run a short jumper wire from Terminal #2 directly to the alternator output (BAT+ terminal). It may work OK that way, but there is no need. This wire is optional. This is the Remote Voltage Sensing Wire and it really should be connected to the main accessory post. The ideal connection would be right where the ignition switch, light switch, and any other accessories are connected to the main terminal block. If you don't hook a voltage sense wire to this terminal, you can simply leave it empty and the alternator will automatically use output voltage.

The #1 and #2 terminals on the Delco 10SI alternator should be connected to your wiring with a special plastic 2-wire connector. You can use individual female crimp-on connectors for each wire, but the proper clip can usually be found in your local auto parts store near the miscellaneous electrical sockets and other replacement electrical parts. Using the proper connector is a more professional solution and also gets you the integral plastic clip that keeps the connector from shaking loose and falling out.

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