Broken wire deep inside a harness

Vehicles have lots of wires running to each and every electrical item. These wires are not draped willy-nilly through the vehicle, that would be a mess, so they are bundled into harnesses. As wires reach their components they break out of the harness like a branch. In German, wiring harness is Kabelbaum, which translates literally to “cable tree”. Considering how the harness is thick at one end and branches off in tangents, cable tree is a very good analogy.

On this job, a Beetle had some serious running problems. The customer had just bought the car and it would shut off at random times. They were getting sick of it, and at their wits’ end they dropped it off at our shop.

The test drive, if you could call it that, revealed that the engine shut off when the transmission was placed in drive. It would idle fine, but put that puppy in drive and it would die. The engine trouble codes were complaining about injector power going away intermittently. Given that, I surmised that a wire was making a poor connection. With an assistant keeping the engine running, I started pulling on the wiring harnesses in the engine bay. One harness in particular would shut the engine off when pulled, and the injector power wire was losing power at the same moment.

Mis-manufactured from the start.

I removed the battery and air filter for access to the harness, opened it up, and found the fault. The wire was broken inside the insulation. On closer inspection the strands were not cut and not fatigued, and the insulation was not marred in any way. It left the factory that way.

Some test equipment was handy in pinpointing the location of the break inside the wire. Once found, I cut the bad section out, soldered in a new piece, insulated the solders with heat-shrink tubing, and reassembled the harness and the rest of the car.

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