Bad Wire Harness Symptoms:  Keep an eye on your vehicle wire harness

Whenever you buy a car, you always look into its compact structuring and durability so that it works for a long time. Here, a critical part of all vehicles is the wire harness, which contributes to these features of a car. You need to focus on maintenance and routine inspection of the wiring so that your accessories do not fail. If not done correctly, the vehicle will cease to function despite giving you durability claims, and companies will do nothing about it. Now, let’s have a closer look at lousy bad wire harness symptoms.

Get Your Free Sample!

Enjoy a free sample worth UP TO $100!
Explore our custom services now. Email us at [email protected] for more details.

The function of the wiring harness

The wiring harness in your car is in charge of keeping all the wires safe from the environment. It works like the live wiring inside your home and comes with similar dangers. Hence, if you expose it, it will malfunction, leading your vehicle to complete disaster. 

The wire harness’s relevance has grown along with the sophistication of modern automobiles. More significant amounts of power are transferred from the battery to the electrical systems in automatic models. In comparison to earlier versions, this calls for an increase in the number of wires and cables that there should be in the harness. 

Causes of wiring harness failures

The harness’ resilience comes from its flexibility, which allows it to absorb shock, although, over time, it may wear and become rigid. 

In addition, it may expose the electrical wires if the harness breaks and pieces fall off. 

Also, temperature changes, bumps in the road, and extensive use can all contribute to the stiffening. 

Harnesses can easily stretch or crack when exposed to extreme temperatures, humidity, moisture, and vibrations.

Incorrect wiring size, an unorganized wiring arrangement, or a faulty crimping method are all areas where mistakes could occur during assembly. 

Large cable harness inside the engine compartment

Caption: Large cable harness inside the engine compartment

Warning signs of wiring harness failures

The first sign of a damaged wire harness is that some accessories will stop working. For example, you might experience fused headlights or non-working screen wipers. Let’s know more details.

An inconsistent or dead battery

Lousy wiring can lead to dead batteries. And it’s possible that the battery isn’t over and perhaps showing a charge, but it just can’t keep its head. The system can’t distribute the power in the car if the battery is dead or isn’t performing correctly. Further, you may suffer from bad experiences.

For example, vehicle lighting relies significantly on the battery, so if the battery dies or there’s a problem with the wiring, your lights dim or flick. You’ll notice this the most when you initially turn on the engine. In addition, your car’s inability to start could be due to a dead battery. 

These symptoms suggest that erroneous electrical impulses are transmitting, making them the primary warning sign of a failing wire harness. 

However, you should know that lousy wiring isn’t usually the cause of a dead battery. There is also a chance that the battery will drain faster than usual, or at least more frequently.

A poorly-functioning engine

An exposed electrical harness causes motor disturbances, such as the random engine working. Further, the failure of one or more of the vehicle’s engines to convert gasoline into mechanical energy prevents the car from moving.

Unexpected acceleration, deceleration, or idling of the motor might be caused by faulty wiring. These may manifest themselves in the form of jerking, stuttering, or lurching during driving.

Electronic Issues

Any time data is lost during transmission; the wiring harness is likely to blame. You might observe strange electrical phenomena and malfunctioning gadgets if the signal is interrupted in some locations. Moreover, it is also possible that the issues also affect the center console of automobiles.

The check engine light is an essential diagnostic tool and a potentially life-threatening warning. Many things may go wrong that would make the check engine light come on, but this faulty or short circuit sensor would be the most likely.

Wire harness in large rubber tubes

Caption: Wire harness in large rubber tubes

Get Your Free Sample!

Enjoy a free sample worth UP TO $100!
Explore our custom services now. Email us at [email protected] for more details.

How do you identify a wrong wire harness?

These symptoms above are not enough to prove the wrong wiring harness. You will follow the following to identify the lousy wire harness.


  • Multimeter
  • Alligator Clips and Wires
  • Test lights
  • Vehicle’s Repair Manual 


  • Using the manual, look for the connectors and relays linked to the non-working components. If there are two or more damaged accessories, look for the shared circuit points and narrow down the inspection points.
  • Now, check if the short circuit hasn’t blown a fuse. You can test it by using a test light. In case of any issue, replace the old fuse and then continue the inspection.
  • Expose the accessory wiring by removing the interior trim panels to check the connections. Be careful as the interior trims might have corrosion and are vulnerable.
  • Take out the wires from the tubing, if any, and inspect the points of damage. Here, you might see worn-out insulation exposing the bare copper wire. These are the points that need repairing.
  • Now, power the accessory and check its voltage with and without load. It will lead you to identify whether there are any grounding issues or short-circuiting.
  • It indicates that the circuit is open and the wiring has problems. Also, check for the continuity of current along the lengths of the wire. If the wiring is wrong, you will have infinite Ohms or OL (out of limit) on the multimeter screen.
  • After finding the problem, you can change a single wire or replace the whole harness with a new loop.
Dusty plugs wires under a rug

Caption: Dusty plugs wires under a rug

Regular Maintenance is Key to avoiding wiring harness failures.

If your wire harnesses face harsh circumstances or treatment, you should inspect them for any signs of damage that could lead to decreased performance. Impact, flooding, tremors, and power surges are all examples of such events. 

Temperature changes can be problematic because they might cause the wire to expand and shrink unexpectedly. As the temperature drops, condensation forms, trapping the moisture and potentially causing water damage if it is allowed to build up. The crimping that holds the wires to the harness assembly might become loose or dislodged if subjected to vibrations or impact.

When should I replace my wiring harness?

Every circuit comprises different components, so wire harnesses are of different types and their damages. Depending on their basic manufacturing and the damage, there are situations when you can go for electrical wiring repair or replace the harnesses.

Looking for a high-quality wiring harness

Generally speaking, a high-quality wiring harness can last a lifetime without causing any issues. Then, how to make one?

Bad Wire Harness Symptoms: Pay Attention to Wiring Harness Design 

Overheating, inappropriate fit or alignment with the use and surrounding electronic parts, and other potentially significant difficulties can soon arise if initial measurements are inaccurate. Moreover, it can also occur if the wiring size doesn’t satisfy the current and power demands of the application.

Bad Wire Harness Symptoms: Carefully Wiring Harness Manufacturing 

Machines fabricate wiring harnesses. Issues with the machine’s wiring harness can arise from improper machine maintenance or inappropriate settings applied by the technician. Also, wrong wire layout, a lackluster connection to the harness frame, and a complicated design are all significant causes of manufacturing errors.

An additional serious problem with wiring harness production is faulty crimping or soldering. There is a potential weak spot in every connection in an electrical system. This risk grows if a novice who doesn’t know which technique to use or doesn’t know how to do it properly does the crimp or solder.

Bad Wire Harness Symptoms: Avoid Poor Quality Materials For Wiring Harnesses

You get what you pay for when it comes to wiring harness issues. When money is tight, teams may use copper alloy instead of OEM-grade copper in places like wire and terminals, reducing reliability and decreasing lifespan. The over molding used to shield the electrical harness from the weather is equally crucial. Poor design methods, which should account for environmental factors while creating items, contribute to insufficient over molding.


A lousy wire harness can lead your vehicle to stop functioning correctly. These problems can arise due to improper manufacturing of the wires initially or rough use over time. Hence, you should look for the symptoms and work on them as soon as they occur. Cloom offers wiring harnesses and cable assemblies to make your connection safe and reliable.

Get Your Free Sample!

Enjoy a free sample worth UP TO $100!
Explore our custom services now. Email us at [email protected] for more details.

Hey, I am John, General manager of Cloom and OurPCB.

I am a responsible, intelligent and experienced business professional with an extensive background in the electronics industry.

Reach me at [email protected] to get a quote for your projects.


Fill in your details and we’ll get back to you in 24 Hours.

contact us


Fill in your details and we’ll get back to you in 24 Hours.