How to Splice Automotive Wires

Use a professional tool and moisture sealant for first-class results

Use a professional crimper and electrical moisture sealant to make quick, solid connections in auto wiring.

By the DIY experts of The Family Handyman Magazine

Splice automotive wires in seconds

Crimp-on wire connectors work well if they’re crimped properly (a 5/16-in.-wide crimp) and sealed (usually with heat-shrinkable tubing). But most cheap crimping tools only make a 1/8-in. crimp, so you’d have to make four of them for a simple butt connection.

Invest about $25 in a professional crimping tool (OTC No. 4497 from Then buy a roll of electrical moisture sealant (3M No. 06147; about $20 from Then just follow the steps in Photos 1, 2 and 3.

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Crimper

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

  • Electrical moisture sealant
  • Butt connectors

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