Proper Wire Splicing Techniques
Splicing—joining two or more wires mid-harness—is common for power distribution or sensor grounds. Doing it incorrectly is the leading cause of intermittent electrical gremlins.
Why We Don't Solder
In standard electronics, soldering is excellent. In automotive environments, it is fundamentally flawed. When you solder stranded wire, the solder wicks up the strands by capillary action. This creates a solid, rigid block of copper and tin.
The point where this rigid soldered section meets the flexible un-soldered stranded wire creates a severe mechanical stress riser. Under the constant vibration of an engine or chassis, the wire will hinge at this exact point, fatigue, and break. Furthermore, high resistance in a failing circuit can generate enough heat to melt the solder.
The Professional Standard: Open Barrel Splices
The correct method is a mechanical cold-weld using an uninsulated open-barrel splice (often called a U-barrel or brass band). When crimped with the correct die, it compresses the wire strands together so tightly that they deform into a solid mass, eliminating all air voids and preventing moisture ingress.
- Strip both wires appropriately (stagger splices if doing multiple in a bundle to prevent a massive bulge).
- Overlap the bare strands inside the U-barrel.
- Crimp using a dedicated B-crimp die designed for splices.
- Cover with dual-wall (adhesive-lined) heat shrink tubing. The adhesive melts and flows around the splice, providing strain relief and 100% waterproofing.
Power (Watts) Calculator
Ultrasonic Welding
For OEM mass production, ultrasonic welding is used. High-frequency vibration rubs the copper strands together under pressure until they fuse. This is the absolute best splice possible, but the tooling costs tens of thousands of dollars, making it inaccessible for the aftermarket.