How to Repair Electrical Wiring in an Engine Harness

by Dan Swords

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Automobile wire harnesses are usually subjected to extreme conditions. The harness is fastened to the engine and chassis, which subjects the harness to excessive heat, cold and vibration. These conditions often cause the wire harness to stretch and contract causing undue stress, sometimes resulting in a broken wire. Corrosion also plays a big part in damaging an engine wire harness. Rainwater from the tires splashes up onto the engine and wire harness, leading to corroded terminals and wires. The corrosion will weaken the copper strands, eventually causing the wire to break. You only need few simple hand tools in order needed to repair a broken electrical wire in your engine harness.

Step 1

Disconnect the negative terminal on the battery. Place the cable and connector in a location so it will not accidentally move and contact the battery post.

Step 2

Locate the two ends of the broken wire. Inspect the wire ends for corrosion. If corrosion is found, remove the damaged copper until clean, shiny copper is revealed. Measure the distance between the two ends, and cut a piece of new wire 3 inches longer than needed. For instance, if there is a 3-inch gap between the wire ends, cut a piece of wire 6 inches long.

Step 3

Use the wire strippers to strip 1 inch of insulation from the ends of the broken wire. Strip 1 inch of insulation from the ends of the new wire. Turn the soldering iron on and allow it to come to temperature.

Step 4

Grab one end of the broken wire and twist the strands in a clockwise direction until they are tight. Twist the strands on the new wire so they are tight. Place the two exposed ends together so they create an “X”. Twist the new wire around the broken wire and wrap it toward the broken wire insulation. Twist the broken wire around the new wire and wrap it toward the new wire insulation. Twist the ends together on the other splice area. Place the soldering iron on the exposed pieces of copper for three to five seconds. Touch the solder close to the solder iron tip. As the copper wire heats up, the solder will be drawn into the copper strands. Continue feeding solder into the wire until the wire strands are covered with copper. Do not blow on the solder connection. Do not move the solder connection while the solder is in its liquid state. Allow the solder connection to cool. Repeat on the other solder splice.