How to Connect Two Auto Electrical Wires

Written by jerry walch Google
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How to Connect Two Auto Electrical Wires
Soldering iron with tips (soldering woodburning kit image by Steve Johnson from

There are many different ways to connect two electrical wires together but they all aren't equally effective. All splicing methodologies aren't equal because of the environmental conditions they must withstand. The biggest enemy of automotive systems, especially the electrical system, is moisture and the minerals that the moist contains. Many of them, especially sodium chloride and salt, are highly corrosive to electrical wiring when the bare conductors are exposed to it. When connecting automotive wiring, you should take steps to seal the connections against the entrance of moisture. One of the best ways to achieve this goal is to combine soldered joints with heat shrink tubing insulation.

Skill level:
Moderately Easy

Things you need

  • Soldering iron
  • Soldering sponge
  • Rosin core solder
  • Wire strippers
  • Diagonal pliers/wire cutters
  • Assorted size shrink tubing
  • Hot air gun

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  1. 1

    Plug in the soldering iron and allow to heat up. Clean the hot soldering iron tip by wiping it on the wet soldering sponge. Once the tip is free of oxidation, "tin" it by applying a fresh coat of rosin core solder. A properly tinned tip will appear a bright silvery colour. A clean, properly tinned tip is the first step in producing good, professional looking solder joints.

  2. 2

    Remove two inches of insulation from the ends of both wires to be spliced/connected together. When using wire strippers, be careful to use the proper gauge-stripping notch to not damage the copper strands. Automotive electrical systems are wired with stranded copper wire for ease of installation and for resistance to damage by vibration.

  3. 3

    Select a piece of shrink tubing slightly larger than the outside diameter of the conductor's insulation and cut of a 2-inch length. Slip the shrink tubing over the wire before proceeding further.

  4. 4

    Hold the two, stripped wires so they crossed each other at a 45-degree angle, one inch from their ends, and then wrap them tightly around each other in opposite directions.

  5. 5

    Solder the splice. Position the soldering iron tip on the underside of the splice and allow the splice to heat up, and then touch the rosin core solder to the top of the splice. The heat will draw the molten solder through and around the splice by capillary action. Never touch the solder to the soldering iron tip.

  6. 6

    Slide the heat shrink tubing down over the soldered splice, centring it on the splice. Give the soldered splice time to cool before sliding the heat shrink tubing over the splice because the hot solder may cause the tubing to shrink before it's properly positioned.

  7. 7

    Using the hot air gun, apply the heat evenly along and completely around the heat shrink tubing, shrinking it down tightly over the soldered splice. Properly applied heat shrink tubing will produce an insulated splice impervious to the elements.

Tips and warnings

  • Be very careful when soldering because molten solder will stick to your skin causing serious burns.

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