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Splicing wires doesn’t seem like it should be rocket science. Touch one bare wire to another, make ’em stay together, and you’re off joyriding in your uncle’s hot rod at 3:00 a.m. But as it turns out, splicing wires can be rocket science, with even NASA formulating standards for how to securely and safely make these connections. Nevertheless, gearheads continue to employ a variety of different wire-splicing methods, insisting theirs is the strongest or the most conductive or the most resilient. So let’s semi-scientifically determine which is the best.

For this test, I’m considering just straight splices—wire to wire—and not any sort of tap, crimp, or plug-in connectors. (Splice versus crimp is a discussion for another day.) I’m also looking at low-voltage automotive wiring, not household or small appliance wiring, and focusing on the splice, not any covering like heat-shrink tubing or electrical tape. While many kinds of splices exist, I’ve narrowed down the test methods to four, all of which are commonly used in auto repairs. I’ll evaluate each on the tensile strength of its mechanical and soldered connections, and I’ll make a note of other attributes, including aesthetics and how the splice affects the wiring itself, all of which is 20- to 22-gauge and comes from my Nissan Leaf’s harness.

Let’s introduce the splices:

Rattail Splice

Instructions: Strip a half-inch to an inch of insulation from both wires. Give each wire’s strands a light twist to keep them from splaying. Lay the wires parallel with the bare ends side by side. Twist the exposed strands together

Wire Color: white

This is the simplest splice, typically capped with an orange wire nut and shoved behind a dashboard. We’ve also seen it referred to as a Pigtail Splice, but aren’t pigtails curled?

Palm Frond Splice

Instructions: Strip a half-inch to an inch of insulation from both wires. Splay each wire’s strands into the shape of a palm frond. Lay one set of splayed strands atop the other. Twist the strands together.

Wire Color: yellow

Also referred to as a Wedding Splice, this method provides many points of contact between the individual strands.

Lineman’s Splice

Instructions: Strip one to two inches of insulation from both wires. Cross the bare strands about a third of the way up. Wrap each bare wire around the other at least three times.

Wire Color: orange

Originally developed for Western Union telegraph lines, the Lineman’s Splice is designed to withstand a lot of tension, and NASA later specified the splice in its technical standards.

J-Hook Splice

Instructions: Strip one to two inches of insulation from both wires. Bend each section into a J shape and hook the wires together. Wrap the tail end of each bare wire around the trunk.

Wire color: red

I’ve discussed this splice before. It’s supposedly the strongest mechanical connection of any wire-to-wire splice. Let’s see if it holds up.

Read on

Palm Rattail Splice