Last week, Hagerty’s Matt Lewis showed us the details of using crimp connectors to join two wires. Now, for our latest DIY video, he demonstrates the proper technique for using solder to join wires.

Soldering wires is the preferred method for professionals that handle automotive electrical components. When joined using solder, a connection is more vibration resistant and has better durability when it comes to corrosion. Nevertheless, many enthusiasts choose not to solder connections, viewing it as time-consuming and difficult compared to other affordable options.

Still, soldering connections is typically the best way to join wires, and after Matt demonstrates the proper way to achieve a solid connection, you will be ready to tackle the wiring needs of that latest project—with a little practice.

For tools, Matt uses his trusty auto-stripper and an affordable soldering iron. He prepares the wire ends by removing a quarter-inch of the shielding, then twists the strands of wire together. The wires can then be situated together by further twisting them, blending them end to end, or wrapping one around the other for a splice. Be sure to place the shrink-wrap tubing on prior to connecting the wires if that is how you plan to seal the connection.

Once the wires are prepared, pick up your warm soldering iron and use it to heat the backside of the bare wires. The solder should be fed into the “cool” side away from the heat, which allows it to be drawn in smoothly by the heat transfer through the wires. Once the connection evenly turns the correct silver color of solder, remove the soldering iron and allow the joint to cool. Once cool, inspect the union to ensure proper penetration of the solder.

The connection should not have any uneven globs of solder, and the solder should penetrate both wires. If this is not the case, trim and re-solder the wires. Once a solid connection is made, seal the connection with shrink wrap or electrical tape to prevent corrosion. And don’t forget to pat yourself on the back.

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