6 Most Common Issues With Wire Harnesses

Need to know what to look for regarding bad wiring harness symptoms? Are you experiencing trouble with your wire harness assemblies? As experienced technicians, we become set in our ways and used to a particular way of doing things. Even though your technicians were trained on the correct methods, once the actions become instinctual they may develop bad habits that can lead to quality issues. Here are six of the most common issues with wiring harnesses, which bad wiring harness symptoms to look for, and what you can do about them.

We’ll start with an automotive example, and then move to the more general realm where wire harnesses are used in many types of white goods, electronics and electrical equipment (think computers, 3D Printers, dishwashers, microwaves, CNC machines, etc. If it has more than one board or electrical component, it will most likely have a wiring harness!).

For cars, RVs and motorcycles, the most common symptom of a bad wiring harness is a dead battery or one which looses charge very quickly and frequently. Another is when the engine either revs up or idles down unexpectedly, or the vehicle lurches / stutters when driving.

Outside of the engine compartment, there are wiring harness for the various lighting and entertainment systems. The most common aftermarket / add-on or custom wiring harness is for installing vehicle-to-trailer wiring. Also called a T-connector, this consists of a simple, plug-and-play electrical device that eliminates the need for cutting, splicing and soldering when installing vehicle-to-trailer wiring. Most vehicles do not come ready to tow. Unless your vehicle has a towing package, it is probably not equipped with a trailer wiring connector. This is where custom wiring harnesses come into play.

Custom wiring harnesses plug into your vehicle’s electrical system using original equipment (OEM) connectors. Our custom wiring harnesses use two or more OEM connectors to plug in at the taillight assembly and provide a standard trailer socket to allow a trailer to be plugged into your vehicle’s power system. This harness provides a 4-way flat connector socket and comes with a circuit-protected converter. Here is a popular example, CURT 56150 Custom Wiring Harness available on Amazon for abut $53.

The next most commonly owner-installed wiring harness is for LED light bars. The Heavy Duty Wiring Harness Kit for Led Light bar 300W 12V 40A Fuse Relay On/Off Switch Relay 14AWG 12FT Length Universal Fitment Light Bar Accessories costs about $13 on Amazon, and a 20 Inch, 126W Led Light Bar / Led Fog Driving Lights which is rated IP67 Waterproof costs about $27 on Amazon.

Let’s explore how wiring harnesses are made, and where companies can run into issues during the initial manufacturing process. Ensuring that you start with correct materials, wires, connectors and configurations will go a long way to guaranteeing the quality of the end product and that it doesn’t prematurely fail after installation.

1. Incorrect Wire Preparation and Staging

Preparing wires for a harness involves: selecting the right wiring product, cutting it to the specified length, and stripping the ends. While this is often done via an automated machine, user error and poor machine maintenance and adjustment can lead to problems. Make sure you are selecting the right size wire, and that the machine is adjusted properly.

2. Poor Wire Harness Layout

Beyond prepping wires, if they are not laid out correctly to be connected to the harness chassis it may not fit in the finished product, or may lead to excessive lengths of wire that will need to be trimmed. Often, creating a form board can help technicians easily identify the wires needed, if any are missing, and where they should be placed.

3. Shoddy Labeling

Probably one of the most common problems experienced with mass produced wire harnesses is improper labeling. One good way to make sure the wire harnesses you receive are labeled correctly is to develop a system that checks for accuracy before the labels are even printed. One good way is to create sample labels for your mock-up or traveler product when you place the work order.

4. Defects in the Crimping Process

Crimping is by far the most widely used method for terminating wire ends. When crimps are not done properly it can lead to short circuits or open circuits within the product. Or, the crimp could spontaneously fail, even if it passed a functional test. Regardless of whether you are hand crimping or using a machine, it is important to ensure equipment is set up correctly for the size of wire you are crimping.

5. Defects in Soldering

There are many issues that can arise when soldering your wires to their terminals. A soldering temperature that is too cold or too hot, poor soldering technique, or using the wrong size of iron tip on the soldering gun can all lead to issues within the circuit, and eventually, the finished product.

6. Wrong or Missing Hardware

As your line works quickly, constantly trying to meet deadlines for production, it can be easy to overlook a wire with a missing terminal connector, or that the incorrect wire is attached to the wrong hardware. Often, the best way around this is to train technicians to double check their work against the assembly specification documents.

For more information on how you can optimize your wire harness assembly line for optimal quality, head over to Assmann WSW Components now!