How To Find a Short in a Car Wiring Harness

Jan 06, 2024

Got an electrical issue in your vehicle? It could be due to a short in the wiring harness. Check it out with these techniques.

In today's society, everything has been modernized with screens and smart technology. This has brought fancy OLED displays and other tech into vehicles to aid drivers, but what happens when they start to malfunction?

While it is possible that an electronic system has failed in your car, it's more likely you have an electrical gremlin. This is commonly due to pinched wires or shorted connections. While locating these issues can be a pain, here are two tools you can use to find an electrical fault in your car's wiring harness (aka wiring loom).

An electrical short is when the electric current flows down the wrong path, creating a low-resistance connection between two conductors. In other words, there is a break in one or more wires, which can lead to intermittent signal(s) and/or power that can cause the electronic system in your car to malfunction.

Electrical shorts are important to address as they can create pesky electrical drains on your battery overnight. They can burn out relays and fuses, and in harsher scenarios, an electrical short can cause an electrical fire.

Luckily, there are some tools to aid you in your electrical nightmare. Among the wide range of equipment you can use are a multimeter and a power probe. These dedicated electrical tools drastically increase your odds of finding your electrical short, while also saving you time.

A multimeter is an electrical instrument that is used to measure current, voltage, resistance, and many other parameters to locate an issue in an electrical system.

Likewise, a power probe is a tool that diagnoses electrical systems on vehicles. Locating electrical shorts is one of the many uses of this tool.

A multimeter is a versatile tool that can be used to find an electrical short. Among the multitude of features a multimeter offers, one of them is continuity testing. Continuity is when there is a completed electrical current, which is imperative for any wiring scenario.

Choosing the wire you want to test, you need to connect the two probes from the multimeter to the two ends of the wire. In an ideal situation, your multimeter will play a constant tone, indicating that you have continuity through the wires. However, if there is not a constant tone, this indicates that you have a problem with that particular wire. Depending on the wire, having continuity is imperative for signal(s), power, or ground(s).

In an unideal scenario, you will only have access to one end of your harness or one end of the connector. Because a multimeter needs a completed circuit to properly test a wire or harness, the previous method will not work. This is where a power probe shines, as it only needs one connection to properly function. Even though there are a variety of power probe types, the method remains relatively the same.

Connect your probe's receiver to the connection you want to test using the red alligator clip. You can use a tiny needle, alligator clips, or another wire to get access to pins inside a harness. As shown above, take your power probe transmitter and run it along the wire/harness you want to test. In a successful test, there will be a constant tone while you run the transmitter down the wire. If there are any disturbances or changes in volume, this indicates that there is a short or break in the wire.

Automotive electrical problems can be a pain even for those who work in the profession. However, with the proper tools and equipment, you are able to speed up your troubleshooting process. Power probes and multimeters are designed for this kind of work, making them excellent devices for diagnosing electrical nightmares. It leaves the guesswork out, which ultimately saves you time and money.

Based on the East Coast, Joshua Ko has been an automotive writer for MakeUseOf for over a year and is a die-hard European car enthusiast. He primarily covers car tips and tricks and DIYs. After graduating from the Pennsylvania State University, he spends most of his time outdoors, writing, or in the garage.