If you’re wiring parts like lights or tow mirrors, extending the wire or splicing the wire to the wiring harnesses can be a useful method to complete the install and can sometimes reduce the amount of wiring. These steps explain how to splice wires in a car the next time you need to extend a wire or splice one in two directions.
How to Splice and Extend an Automotive Wiring Harness or Electrical Wire
How to Splice Wires in a Car in 5 Steps
- Wire Cutters
- Wire Strippers
- Butt Connectors
- Electrical Tape
How to Splice or Extend an Automotive Electrical Wire
- Pick a Spot on the Electrical Wire
Pick a spot on the electrical wire near the connector. The spot does not need to be close to the connector.
- Cut the Wire
Cut the wire with wire cutters
- Slice the Outer Sheath
Cut the outer sheath with a razor blade
- Strip the Insulation
Strip the insulation from the ends of the wires an inch or two with a wire stripper
- Twist the Copper Core
Twist the copper wire core ends
- Repeat These Steps for Additional Wiring Harnesses or Wire Extensions
Repeat the steps above for any wire extensions
- Twist Any Additional Wiring Harnesses or Wire Extensions Together
If you’re splicing or branching a wire in two different directions, twist any corresponding wires on the branched wires together. For example, if you’re splicing a wire to two wiring harnesses, twist the copper cores of each matching wire on the wiring harnesses together. In the picture below, we twist the copper cores of the red wires together and the copper cores of the black wires together.
- Connect a Butt Connector to Each Branching Wire
Connect the double wire side of a butt connector if two wires are connected, like in this case. Twist a butt connector on as tight as possible to each wire that will branch off.
- Crimp the Butt Connector to Each Branching Wire
Crimp the butt connector to the now-branched wire. Tug on the butt connector to confirm it’s connected tightly
- Connect the Wire Extension
Connect the wire extension to the butt connector and twist it in as far as possible
- Crimp the Butt Connector to the Wire
Crimp the butt connector to the wire extension
- Apply Electrical Tape to the Extended Wire
Seal electrical tape to the extended wire to keep the wires connected and to protect the wires from outside elements