(These buttons "toggle" their respective harness/wire on and off.)
Harness Color Codes

Color codes taken from Willys 1945 Maintenance Manual (except where noted: (*)).

Right Side Harness

Black - 3 White tracers (12 ga.): Starter switch to Ammeter "Bat" (+) terminal
Red - 3 White tracers (12 ga.): Voltage Regulator "B" terminal to Ammeter "Gen" (-) terminal
Red - 3 White tracers (12 ga.): Ammeter "Gen" (-) terminal to Light Switch Circuit Breaker
Black - 2 White tracers (14 ga.): Ignition Coil primary to Distributor

Main Harness

Black - 2 Red tracers (14 ga.): Ammeter "Bat" (+) terminal to Horn (either terminal)
Blue - 3 White tracers (12 ga.): Light Switch "H" terminal to Dimmer switch input terminal
Red - 1 White tracer (16 ga.): Light Switch "R" terminal to Chassis harness tail light wire coupler
Green - 1 White tracer (16 ga.): Circuit Breaker output to Chassis harness brake light wire coupler
Red - 1 White tracer (16 ga.): Circuit Breaker output to dash light switch
Yellow - 1 Black tracer (16 ga.): Light Switch "A" terminal to Junction block lower terminal
Blue - solid (16 ga.) (1): Hi-beam indicator lamp to Dimmer switch hi-beam terminal
Red - 3 White tracers (12 ga.): Dimmer switch hi-beam terminal to Junction block upper terminal
Black - 2 White tracer (14 ga.): Dimmer switch lo-beam terminal to Junction block center terminal

Chassis Harness

Red - 1 White tracer (16 ga.): Main harness tail light wire coupler to tail light 3-way coupler
Green - 1 White tracer (16 ga.): Main harness brake light wire coupler to brake light switch
Green - 1 White tracer (16 ga.): Brake light switch to brake light 3-way coupler
Black - 2 White tracers (14 ga.): Horn (other terminal) to horn brush (on steering column)

Generator/Regulator Harness

Red - 3 White tracers (12 ga.): Generator Armature to Regulator "A" terminals
Green - 2 White tracers (14 ga.): Generator Field to Regulator "F" terminals
Black - 2 White tracers (14 ga.): Generator ground terminal to Regulator chassis/fender bolt

Head/Marker light Wires/Harnesses

Red - 2 White tracers (14 ga.): Hi-beams to Junction block upper terminal
Yellow - 2 White tracers (14 ga.): Headlamp chassis ground
Black - 1 White tracer (16 ga.): Lo-beams to Junction block center terminal
Yellow - 1 Black tracer (16 ga.): Marker lamps to Junction block lower terminal

Tail/Brake light Wires/Harnesses

Red - 1 White tracer (16 ga.): Tail lamp filament to Chassis harness 3-way coupler
Green - 1 White tracer (16 ga.): Brake lamp filament to Chassis harness 3-way coupler

Individual Wires (under dash)

Black - 2 White tracers (14 ga.): Ammeter "Gen" (-) terminal Ignition/Coil switch (+) terminal
Green - 1 White tracer (16 ga.): Ign/Coil switch (-) terminal to Fuel Gauge "Ign SW" (+) terminal
Red - 1 White tracer (16 ga.): Fuel Gauge "GA" (-) terminal to Gas tank sender
Black - 1 Red tracer (16 ga.) (2): Dash light switch to dash (Instrument) lamp

Notes:

  1. From repro harnesses (not listed by Willys).
  2. From an original harness (not listed by Willys).
Comments

All color codes and wire gauge sizes (except where noted) conform to Willys published documentation, and have been verified from actual original harnesses.

Harness lengths & distances between pigtails are NOT in proportion to a real harness.  They have been adjusted to fit the drawing area for clarity.

Component locations are NOT as found on the vehicle.  They have been spread out for clarity.

Component markings are original.  If you have aftermarket/repro components, they may have different markings.

Concessions to graphics simplicity:

  • "Front Lights" are all grouped together, instead of separately (2 wires for marker lights and 2 loom bundles for headlights).  These wire connections should be obvious.
  • The "Single Tail Light" originally did not have separate pigtails.  The 2 wires in the "Chassis" harness plugged directly into the light socket.
  • The 3-way couplers for "Dual Tail Lights" are NOT original to Willys, but are used in repro harnesses (originally, the passenger side light wires plugged directly into the drivers side light socket).
  • Only the column brush horn wire is shown.  The connection for gearbox bottom exit wire is the same.
  • The high beam tell-tale wire is always shown.  If your harness doesn't have one, ignore the all-blue wire (it should be obvious).

BEWARE ! !  Not all repro harnesses are correct!

  • Wire from headlight switch to dimmer switch should be 12 ga.
         (3- white tracers)
  • Hi-beam wire from dimmer to junction block should be 12 ga.
         (3- white tracers)
  • Lo-beam wire from dimmer to junction block should be 14 ga.
         (2- white tracers)

In the questionable repro sets, the Main harness headlight wires (from light switch to dimmer to junction block) are 2 ga. too small.  ie, 16 ga. (1 tracer) instead of 14ga. (2 tracers) and 14ga. (2 tracers) instead of 12ga. (3 tracers)

If you've converted to 12v electrical system, it's not an issue.  BUT IF YOU'RE STILL AT 6v, THIS IS MARGINAL AT BEST, POTENTIALLY UNSAFE!