how to find a short in a car

How to Find a Short in a Car – A Guide

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The wiring system in cars these days has become very complex. In addition to a 12V battery, a starter motor, and ignition switch, modern vehicles also include things like air conditioning compressors, power steering pumps, alternators, and even fuel injectors.

All these systems require their own electrical connections. This means that if one wire comes loose, the whole system can fail. It is important to check your vehicle’s wiring regularly.

Essentially, a short circuit happens when the electrical current flows through the wrong path, or the wires connect to each other at the wrong place. If a short circuit occurs in the battery, it may cause fire or explosion. 

Many factors can lead to a short circuit. It can happen due to a loose connection, damaged wire, faulty wiring harness, broken wire, or bad contact between the terminals. In this article, we will teach you how to find a short in a car.

What is an Electric Circuit in a Car?

how to find a short in a car

Many components in your car need electricity to function properly. Your engine provides power to the driver-train, but not to every component directly. That’s where the car battery comes in.

An automobile’s battery supplies juice to the various electrical circuits in your car. Depending on how many features your car has, the circuitry implemented in it could get extremely complicated.

Sensory Circuits

These sensors are usually not necessary for the basic functioning of the car. They do provide important information on the different components connected to the control module. 

These range from telling you about the air pressure in each tire, to sensors that can perceive the car’s speed. It is important to note that a short circuit in the sensory system could not only damage these sensors, but other systems of the car as well.

Attention should be paid to the wire harness of this system, regardless of the fact that these sensors are superficial to the running of a car. It is best practice to get the short circuit fixed before it can cause any major system failures.

Actuator Circuits

These devices work in close tandem with sensor systems. The real-time input of different parts of the car go into the sensors. These feed data into the control module, which decides if anything needs to be altered. 

Control modules will then instruct the actuator motors to perform a certain action that will bring about normalization in the sensory input.

Actuators are among the most basic components of a car’s circuitry. They perform the most basic functions – like turning off the headlight knob, or lowering the air conditioning temperature. In these scenarios, actuators actually receive input from you, the user.

A short circuit in actuator systems will be really easy to detect. Every time an input doesn’t result in a physical output from the car, you should suspect a problem in actuators. This can be due to a short circuit, a blown fuse, or a busted actuator motor.

Primary Circuits

These are among the most critical and essential circuits in a car. Located, in most cases, behind the glove box of a car, it consists of the connecting wire between the Engine Control Module (ECM) and Engine Coolant Temperature (ECT).

The coolant temperature sensor gives varying voltage to the control module, depending on how hot or cold the engine coolant is. 

If the voltage given is more than normal, the high-temperature indicator light may turn on. Essentially, this means that the engine coolant is running high, and the owner must take appropriate countermeasures.

An always-on check engine light could, therefore, suggest a shorted ECT or a fuse that has stopped working. It could also simply be due to bad wiring to the LED. Nevertheless, it begs diagnosis before the car actually heats up and fails to indicate it to you.

Types of Short Circuits

There are 2 types of short circuits, and neither of them is any more desirable than the other.


This type of short circuit occurs when electricity is grounded. A ground circuit can occur when the electric current passes from the wires to the metal body of the car. 

Most often this is an issue with the insulation of the cables in the car. Chafing of the insulation will expose the wire inside, which leads to a grounding if it accidentally comes into contact with the body.


These are the sparking sort of short circuits. Usually, their cause lies within the wire harness, in which multiple cables are bundled together. When two exposed wires come into contact with each other, a spark ensues. 

The electrical current will travel to unintended parts, leading to, for instance, lights randomly turning on when you press the horn.

How to Find a Short in a Car

finding short in a car

There are multiple ways you can locate a short in your car. But first, you need a few tools. These tools come in the form of a multi-meter and an EWD. The latter is an Electrical Wiring Diagram of your vehicle’s circuit system. 

With the help of this, you can link every wire to its respective system, which will make the diagnosing process easier.

Check For Any Visible Faults in the Wires

Step 1

Disconnect the battery from the wiring system. You wouldn’t want to get an electric shock while you’re working, would you?

Step 2

Pop open the hood of the car and locate the fuse box. Remove the fuse block panel cover to expose different fuses. Alternatively, you can access it from the dashboard, if that’s more to your liking.

Step 3

Disconnect the wires from their connections and scan them for any defects or exposed wiring. The EWD will help you identify which wires go to which system. 

You can then work only on the wires that belong to the circuit causing problems. It may be necessary to open a few panels to access the hidden wires.

Use The Multimeter


A far easier method is to use a multimeter tool if you have one on hand. Once you have gained access to the fuse-box, set the multimeter to mV (milliVolt). Now take the probes of the multimeter and place them on the connection points of each individual fuse.

A short will be indicated by a voltage difference between the two probes. Essentially, this means that there is a resistance across the probes, hence a voltage reading greater than zero is shown on the multimeter.

Keep checking for a voltage reading across every fuse until you’ve located one. Take it out of the fuse socket and check if it is busted and causing the voltage drop. If it’s fine, then you’ve potentially located the circuit which is short.

Pull out your EWD and confirm if the shorted circuit corresponds to the problematic system of the car.

Trace the Cable

Once the cable has been located, trace it back to its actual component. This is going to be a hassle, as the farther it is, the more panels you’ll have to open to get access to the wire. In this step, you need to assess where the cable is damaged.

If you can’t trace the wire’s path, you can use a circuit tester kit. These come with a radio and transmitter which will help you discern the path it takes.

Most often, the short occurs close to where the wire connects with the components. Before you start dissecting the car, carefully examine the component’s connection. A short would be identifiable by two cables joined together, blacked cable insulation, and even a burning smell.

How Do You Fix the Short?

Now that you’ve located where the wire shorted, the next step would naturally be to fix it. If you’re lucky, then it was just a busted fuse and it shouldn’t take you a lot of time.

In more complicated situations, you may have to replace the entire cable that’s going to the component. Sometimes the short will even kill the component, which will require a replacement.

How to Find a Short in a Car: Conclusion

Whenever electrical circuits are involved, short circuits will follow soon after. Sometimes it’s because of a bad connection, other times it is caused by old and worn-out wires. In both scenarios, diagnosing the short and identifying it is just the first step. 

Even though a short circuit is a nuisance, you have to fix it because it can lead to bigger problems down the road.

In this article, we discussed what electrical shorts are and their different types. We also talked about the basic categories of circuits inside a modern vehicle. This article guided you comprehensively on how to find a short in a car, using different tools.

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