want free jegs gear?

Comment on any of our posts with your expertise and we'll send you a bag of JEGS schwag.

Learn More >

Installation Instructions for 10400 Universal Wiring Harness 


Please read completely through these instructions before starting this installation. 

Check to make sure that the wiring harness kit includes all components (see Appendix A). The kit includes the prewired fuse block and six poly bags with different components of the wiring harness and connectors in each bag. Each bag has a sheet w/ photos of the components in the bag for easy identification. 

The JEGS universal wiring harness is designed for use in most cars or trucks that have the engine mounted in the front of the vehicle and can mount the fuse block under the dash. Since this harness can be installed in many different types of vehicles, the installation may require some modifications to suit the options and features of your vehicle. When using aftermarket accessories and equipment, use the wiring diagrams provided with those products (instead of this manual). 

This kit comes with specialized GM connecters for the steering column (ignition switch, horn, and turn signals), headlight switch, high/low beam dimmer switch, brake light switch, backup switch, and alternator. This wiring harness can be used on vehicles that do not use these GM style connectors. The GM connectors can be omitted and replaced with other connecters where needed. If you need different connectors, you may want to remove and reuse any special connecters from your old wiring harness (if available and they are in good condition). 

If you need new switches, you may want to use GM style switches since it will be easier to hook them up using the wiring connectors that are included with this harness (i.e. headlight switch, or high/low beam dimmer switch - see Appendix B). This is not required since any type of OEM style switches will work with minor wiring modifications. 

The ignition switch can be mounted on the steering column (GM connectors included), or a universal ignition switch can be mounted on the dashboard. 

The wiring included in this wiring harness is colored and labeled for easy identification of each wire. 

General Guidelines and Recommendations
  • Disconnect both battery cables before starting this installation. 
  • Install main ground cables that go between the chassis and engine and between the engine and body. These ground cables are not included with this kit. 
  • Ground all accessories. Ground wires are not included with this kit. 
  • All Ground connections must be made free of dirt, rust, or paint (metal to metal connection). 
  • Route all wiring before cutting the wires to length and crimping on the terminals to make the connections. The wiring is provided in generous lengths and will need to be custom trimmed to fit your vehicle. 
  • Route wiring away from sharp edges, heat, and any moving parts like fan belts, steering gear, driveshaft, hood latches & hinges, and the exhaust system. 
  • Use a grommet whenever wiring is passed through a sheet metal or fiberglass panel. 
  • Cover the wiring with Convoluted Tubing or Flexbraid to protect the wiring. 
  • Fasten the wiring down with clamps and cable ties. 
  • Use insulated connectors or heat shrink tubing over the connections. 
  • Always use the correct terminal size for the gauge of wire. 
  • Do not over-crimp the terminals. 
  • Use the wiring diagrams provided with aftermarket or specialty accessories (instead of the wiring diagrams provide in this instruction sheet).
  • Do not skip around – start a section and finish it. 
  • Use the worksheet since it will save time and document the wiring on your vehicle. 
  • Don’t forget that these are only general instructions and that you may need to make some modifications for your vehicle.

Keep these instructions when you are finished. You may need to refer to them later and review your notes when making changes or repairs to your vehicle. 


All electrical devices must be connected (grounded) electrically to the negative battery post. Some devices have a ground wire, and some ground through their case where it is mounted to the chassis, body, or engine. Ground wires must be large enough to handle the current flow and generally large wires are recommended. 

Most vehicles have a steel body and frame which are used as the ground. Components are bolted to the engine/body/frame, or their ground wires are attached to the engine/body/frame. 

Fiberglass body cars cannot use the body as a ground and must run individual ground wires from all components to the frame or engine. In many situations the ground wires must be added to connect the case of each component to the engine or chassis. 

Heavy gauge battery cables and grounding straps (555-10302) must be used between the engine/body/frame and the negative battery terminal. The best place to attach the ground strap to the engine is on a starter motor bolt to make sure the starter gets adequate voltage. 

All ground connections must be metal to metal connections that are free of dirt, rust, or paint. 

Ground wires are not included with this wiring kit. 

Vehicle Preparation 

Disconnect both battery cables from the battery. Mount all electrical accessories and switches in their final positions. The engine/Transmission and all other electrical components must be installed to determine the wiring length and to make the appropriate connections. 

Wiring Worksheet 

The wiring for a typical vehicle is normally divided into four basic sections (Front Section, Steering Column Section, Dash Section, and Rear Section). The wiring worksheet (see Appendix C) included with this instruction sheet lists the wires that are normally used in each of these sections. The wiring diagram that is also included in this instruction sheet shows where each wire goes. 

Review the worksheet while looking at your vehicle. It may be necessary to move some wires from one section to another. For example, the ignition switch wires may need to be moved from the Steering Column section to the Dash Section if you plan to install the ignition switch on the dash instead of the steering column. 

Go through the worksheet and compare the list of wires to your application and note if each wire will be Used, Moved, or Removed. This will be different for each vehicle since they don’t all have the same accessories. Before marking wires to be removed, consider accessories that you may want to add at a later time. Also consider accessories that have not been provided for in this wiring kit. 

Optional Accessories: 

Some of the circuits on the fuse block are designed for optional accessories (some of the common optional accessories mentioned below are shown in the wiring worksheet and wiring diagram). 

A1 – This circuit has power when the ignition switch is in the “accessory” or “on” position. This circuit can be used for a fuel pump relay or electric fan relay. In most cases a relay is needed since this is a 10 amp circuit and may not have enough amperage to run these accessories w/o the relay. Use fuel pump relay kit 555-10564, or cooling fan relay kit 555-10559. 

B1 – This circuit can be used for power locks or other circuit that needs power all the time (even when the vehicle is off and the key is not in the ignition). 

B2-Mem – This circuit can be used for the radio memory, clock, or other circuit that needs power all the time (even when the vehicle is off and the keys are not in the ignition).

Key/PCM – Use for accessory that needs power when the ignition key is in the “on” position. 

Key On – Use for an electric choke or other accessory that needs power when the key is in the “on” position. 

If you use an extra circuit for another accessory, make sure that the wire is the proper size and the fuse is the proper amperage for that accessory. Document any changes that you make on the worksheet so that you can refer to this information later when modifying or repairing your vehicle. 

Prepare the Harness for Installation 

Spread out the harness on a large work area (i.e. the floor next to your project car). Start with the fuse block and organize the wires that are attached to it into the four groups (Front Section, Steering Column Section, Dash Section, and Rear Section). Review the wiring worksheet and wiring diagram to assist with this process. Use cable ties to organize the wiring into these four groups. Not all the wires shown in the wiring worksheet or wiring diagram will be attached to the fuse block since some are included in the poly bags (these wires will be added later). 

Any wires that were marked “Remove” on the wiring harness can be removed at this time. Do not cut off any wires unless you are sure you will never need them. 

Mounting the Fuse Block 

The fuse block should be mounted under the dash on the driver’s side of the vehicle. The fuse block must be securely mounted on a flat surface. The fuse block must be mounted away from moving components (i.e. pedals & steering shaft). Find a suitable location that is accessible for inspection and replacement of fuses. Make sure the heavy IGN, ACC, and BAT2 wires will reach the ignition switch. Mount the fuse block using bolts or screws using the holes at the outer edge of the feet on the fuse block. 

Note where the front section wires exit the fuse block and find a suitable location where these wires can go through the firewall and into the engine compartment. Find a location where the wiring won’t interfere with other components and will be away from heat or moving components that may damage the wire. At that location, drill a 1 ¼” hole and install the grommet provided in the kit. 

Remove the cable ties from the Front Section wires and pass them thought this grommet into the engine compartment, one wire at a time. 

Route the Rear Section wires to the back of the vehicle inside along the floor. The wires can be taped to the floor or run under the driver’s side door sills. These wires need to be routed where they will not be stepped on and where the seats or seat track will not interfere with them. 

Route the Steering Column Section and Dash Section wires to the corresponding area of the vehicle. Do not make any connections at this time since more wiring will be added from the kits in the six poly bags. 

Ignition Kit 

Add the wiring from the “Ignition Kit” (poly bag) to the harness. The purple “START” wire runs between the ignition switch and the small start (S) terminal on the starter solenoid. This wire comes with the GM steering column connector for the ignition switch. This connector is used if you have a GM steering column. Three additional wires from the harness will be installed into this connector (use the 56 Series Terminals to make the connections). Refer to the wiring diagram to see the positions of each wire in this connector (ACC, BAT2, IGN wires). Cut off this connector if you don’t use the GM steering column or use a dash mounted ignition key switch (see the Alternate Ignition Switch detail on the Wiring Diagram). A neutral safety switch can be added in the purple “START” wire if desired (optional). 

This kit comes with the fusible link (FL-1, 1mm) (w/ Yellow Butt Connector) that must be installed on the red “BATTERY FEED” wire where it connects to the large terminal on the starter solenoid. 

This kit comes with the grey power connector for the GM HEI distributor. Add this connector to the end of the DK Blue “IGN PWR” wire where it connects to the distributor. Omit this connector if it is not needed. 

Refer to the drawings in Appendix E, F, and G for additional information the connections for common GM, Ford, and Mopar ignition systems.

Alternator Kit 

This kit includes the alternator harness with connectors for the Delco alternator and a fusible link. 

The fusible link (FL-2, 2mm) must be used on the end of the large red where it connects to the large battery stud on the starter solenoid. The white wire connects to the TAN “GEN LMP” butt connector near the fuse block. This harness can also be used with a one wire alternator, but cutting off the small red wire (push back the boot and cut it close to the large terminal – omit the 2 position connector and the small red and white wires. 

Other types of alternators and generators can be added by cutting off the GM connectors and using the same wires. Review the Charging System drawings in Appendix E, F, and G for common GM, Ford, and Mopar wiring diagrams. 

Headlamp & Dimmer Switch Kit 

Add the wiring harnesses included in the “Headlamp & Dimmer Switch Kit” (poly bag) to the wiring that is already installed in the vehicle. 

The larger harness in this poly bag is the main headlamp harness w/ the large black GM style headlight switch connector. Review the wiring diagram and install the harness w/ the large connector at the light switch and the other wires where they need to go to make the connections. 

The headlight switch must be mounted to metal or an additional ground wire is required. Connect the RED “HLS FEED” wire from the fuse block to the “HLS FEED” wire on this harness w/ a butt connector. Also connect the YELLOW “PARK FEED” wire from the fuse block to the “PARK FEED” wire on this harness. 

The Dimmer switch harness has the GM style connector for a floor mounted high / low beam pushbutton style switch. Connect the LT BLUE “DIM SW” wire to the center connector as shown in the wiring diagram. 

The “TAIL/LICENSE” harness will connect to the LT GREEN “PARK-SIDE” wire that comes out of the connector for the light switch. 

Route the appropriate wires to the front and rear of the vehicle and make the connections for the parking lights, tail lights, dome light, and headlights (head lamp connecters are included in this poly bag). Note that the switch in the dome light is in the ground side of the circuit. 

Turn Signal Kit 

The Turn Signal Kit (poly bag) includes the wiring harness w/ a special connector for a GM style steering column. Many aftermarket steering columns also use these same connectors (i.e. Ididit and Flaming River). The special adapter allows the use of any steering column (or turn signal switch) and fits into the connector on the turn signal harness. 

Many of the wires needed in this GM style connector are already attached (these wires go to the front turn signal lamps, brake lights, indicator lamps in dash, and the horn and horn relay). 

You will need to add 3 wires to this connector. These are the BROWN “HAZ FLSHR”, PURPLE “TS FLSHR”, and WHITE “STOP SW” that originate from the fuse block. Determine where the steering column connector will be located and cut the flasher wires to the proper length. Strip the wires and crimp on the special signal terminals on the ends and solder. Insert the PURPLE “TS FLSHR” wire into the “L” opening on the connector, and the BROWN “HAZ FLSHR” into the “K” opening on the connector. 

Run the WHITE “STOP SW” wire from the fuse block to the brake light switch using the GM style connector and then from the other side of the switch to the “P” opening on the turn signal plug (use the special crimp signal terminal and solder). 

Keep in mind that most vehicles use the same element in the tail light bulb for the brakes and turn signals. This is why power from the brake light switch must go to the turn signal switch. If you have a 3rd brake light then run a separate wire to that light from the WHITE “STOP SW” wire after the brake light switch. If you have separate bulbs for the brake lights, then use the same wire as the 3rd brake light and run it to the brake lights on both sides of the car.

The horn button is in the ground side of the circuit. The BLACK “HORN SWITCH” wire on the turn signal harness must be attached to the BLACK “HORN SWITCH” wire that is attached to the Horn Relay that is mounted on the side of the fuse block. The orange horn wire attaches directly to the horn(s) using the small black connectors in this kit. Most horn buttons have only one wire and the body of the button is grounded. If the horn button has two wires, then wire one to ground and the other to the relay (through the steering column connector). 

Most early Ford vehicles do not use a horn relay. These systems use power from the fuse panel to the switch and then to the horn (omit the horn relay and use a Ford service manual to wire this type of horn system). 

Connect the turn signal indicator connectors to the dash lights and then run the turn signal wires to the front and rear of the vehicle and make the connections to the lights. 

The turn signal indicator lights and front turn signals will require a minor modification for installation. The fix is to cut the “DRV T SIGNAL” LT BLUE wire and “PASS T SIGNAL” DK BLUE wire at the small connectors where they attach to the turn signal indicator lamps on the dash. Be sure to tape up the wire where it is cut at this small connector. The loose wires that have been cut should be routed to the front of the vehicle and attached to the turn signal lights. 

The turn signal harness can be used on any type of steering column or turn signal system. This kit includes a special adapter that fits into the steering column connector. Crimp and solder the special male terminals on the wires in your steering column and insert them into the special adapter. This adapter is then snapped into the steering column connector. Refer to the steering column wire colors shown in Appendix E (GM), F (Ford) & G (Mopar), or your service manual for other vehicles. 

Gauge Wiring Kit 

The Gauge Wiring Kit (poly bag) includes all the individual wires need to wire most gauges. Refer to the gauge wiring diagram – Appendix H. 

The gauge lights connect to the headlight switch and have a remote fuse that is not in the fuse block. The brown GM HEI connector for the tachometer is included with this kit. The BLUE “INST” wire is the gauge power wire. Wire the gauges as shown in the drawing. 

This wiring kit is not recommended for use with an Ammeter (use a Voltmeter instead). 

Final Connections 

Go though the wiring worksheet and connect any accessories that have not already been connected. Check off each connection on the worksheet as it is completed. Check all wires and make sure they are connected to the appropriate accessory. 

Use cable ties to group the wires together and at points where the wires branch off from the harness. It is also suggested that Convoluted Tubing is used to protect the wiring (not included with harness kit – part number 555- 10665). 

At this point there should not be any loose or unused wires left. If there are any unused circuits wrap them up and protect them in a manor that won’t allow them to create a short. 

Testing and Final Connections 

At this point you should have all the wires connected. All that remains is a simple start up procedure. Start by turning off all accessories. Place the ignition switch in the off position and close all doors on the vehicle. Now connect the Positive battery cable. Before connecting the Negative cable, check for current draw. This is done with a test light connecting between the negative battery post and the negative battery cable. No Light = No Draw. If you have no draw or just a really dim light, it is safe to connect the Negative battery cable, and start checking the system. If there is a draw there must be a short to ground and this issue must be corrected before you proceed to test the system. 

Appendix A 

This wiring harness kit includes the prewired fuse block assembly (w/ fuses, hazard flasher, turn signal flasher, and horn relay) and six individual poly bags (the contents of each bag are shown below).

Wiring Kit

  • Firewall Grommet – 1-7/8” (fits 1-1/4” hole) 
  • Cable Ties – 100 pieces 
  • GM Backup Connector – Black 2 Pin 
  • (2) 56 Series Crimp Terminals (for Backup Connector) 
  • Solder Roll 

Alternator Wire Kit (See Appendix E, F, G) 

  • GM Delco Alternator Harness w/ Connectors 
  • Fusible Link (FL-2, 2mm) – Dark Grey Wire w/ Ring Terminal on End 

Headlight & Dimmer Switch Kit (See Main Wiring Schematic) 

  • Headlight Switch Harness w/ GM Style Headlight Switch Connector 
  • (2) Headlamp Connectors w/ Wire Pigtails 
  • Tail Light / License Light Harness 
  • Dimmer Switch Harness w/ Connector for GM Style Switch 
  • Female 56 Series Terminal (for Dimmer Switch Connector) 
  • (4) Dead End Splice 
  • (2) #10 Ring Terminal 

Gauge Wiring Kit (See Appendix H)

  • Gauge Wires 
  • GM HEI Tachometer Connector (Brown) 
  • Female 56 Series Terminal (for Tach. Connector) 
  • (16) #10 Red Ring Terminals 
  • (16) #10 Blue Ring Terminals 

Ignition Wire Kit (See Appendix E, F, G)

  • Ignition (Start) Harness w/ GM Column Connector and ring terminal 
  • GM HEI Distributor Power Connector (Grey) 
  • (3) Heavy Duty Crimp Terminals 
  • (3) #10 Ring Crimp Terminals 
  • Fusible Link (FL-1, 1mm) – Grey Wire w/ Ring Terminal on End 
  • Heat Shrink Tube 
  • (3) 56 Series Crimp Terminals (standard) 
  • Solder 

Turn Signal Wire Kit (See Main Wiring Schematic)

  • Turn Signal Harness w/ GM Steering Column Connector 
  • (2) Horn Connectors (Single Pin) 
  • Turn Signal Adapter 
  • GM Plunger Style Stop Switch Connector (Two Pin) 
  • (4) 56 Series Crimp Terminals (Horns and Stop) 
  • (4) Turn Signal Connector Crimp Pins 
  • (10) Adapter Crimp Pins 
  • (3) #8 Red Ring Terminals 
  • Red Bullet Crimp Terminal (Horn) 
Appendix B 

Optional JEGS Switches & Accessories (not included – available separately)

  • 555-11100 JEGS Universal Dash Mount Ignition Switch w/ Keys 
  • 555-11110 JEGS Universal GM Style Headlight Switch 
  • 555-11115 JEGS Universal Windshield Wiper / Washer Switch 
  • 555-11125 JEGS Universal GM Style Headlight Dimmer Switch (Floor Mount) 
  • 555-63070K JEGS Brake Light Switch w/ Wiring Pigtail 
  • 555-10310 JEGS Push Button Switch
  • 555-11121 JEGS Door Jamb Switch 
  • 555-10705 or 555-10700 JEGS Crimp Connector Set 
  • 555-10630 JEGS Heat Shrink Tubing Kit 
  • 555-10665 JEGS Convoluted Tubing Kit 
  • 555-10658 JEGS Flexbraid Wire Cover Kit 
  • 555-10360 JEGS Grommet Assortment Kit 
  • 555-10564 JEGS Fuel Pump Relay Kit 
  • 555-10559 JEGS Electric Cooling Fan Relay Kit 
  • 555-10302 JEGS Ground Strap 
  • 555-W5369 JEGS Mini Blade Fuse Kit 
  • 555-11050 JEGS LED Indicator Lamp – Red - 1/8” Bulb 
  • 555-11051 JEGS LED Indicator Lamp – Blue – 1/8” Bulb 
  • 555-11052 JEGS LED Indicator Lamp – Amber – 1/8” Bulb 
  • 555-11053 JEGS LED Indicator Lamp – Green – 1/8” Bulb 
  • 555-11060 JEGS LED Indicator Lamp – Red – 5/16” Bulb 
  • 555-11061 JEGS LED Indicator Lamp – Blue – 5/16” Bulb 
  • 555-11062 JEGS LED Indicator Lamp – Amber – 5/16” Bulb 
  • 555-11063 JEGS LED Indicator Lamp – Green – 5/16” Bulb 
  • 555-11070 JEGS LED Indicator Lamp – Red – 1/2” Bulb 
  • 555-11071 JEGS LED Indicator Lamp – Blue – 1/2” Bulb 
  • 555-11072 JEGS LED Indicator Lamp – Amber – 1/2” Bulb 
  • 555-11073 JEGS LED Indicator Lamp – Green – 1/2” Bulb 
  • 555-75050 or 555-75051 JEGS Self Fusing Silicon Tape 
  • 555-80575 JEGS Wire Crimping Tool 
  • 555-80573 JEGS Cut and Pull Wire Stripper Tool 
  • 555-10669 JEGS Convoluted Tubing Installation Tools (3 piece kit)
Appendix C 

Front Section

Steering Column Section

Dash Section

Rear Section

Appendix D 

Reference - Circuits & Fuse Sizes

Appendix E 


Appendix F


Appendix G 


Appendix H 


Customer q:



No items found.

car specs

social media

exterior modifications
interior modifications
Posted on
May 10, 2018
Instruction Guides

Psst! Want a chance to win FREE SCHWAG? Comment on this post and click here for details on the JEGS Comment Contest >

You Might Also Like

Follow us on Instagram to get notified about new products and discounts

Follow Us