What Are Fusible Links? Plus Symptoms, How to Check, and How to Replace

Fuel system leaks are among the common causes of car fires, but they’re not the only hard-to-spot culprits. Short circuits also pose the same danger. Various issues can cause them, from damaged wires to loose connectors, and they’re difficult to pin down because wires run throughout the vehicle.

Fortunately, there’s a small and weak wire that helps protect the wiring system in the event of short circuits: the fusible link.

What Is a Fusible Link?

Fusible links are not copper-strand wires, but are a special alloy wired with non-flammable  Hypalon® insulation. They’re around six to nine inches long and are smaller than the wires of the circuits the fusible links protect.

These links are the first to melt in case of excessive current flow, opening the circuit to prevent a fire hazard. The non-flammable insulation also suppresses any spark that may lead to a fire hazard. You can find links near or next to the battery to protect its wiring.

Symptoms of a Bad Fusible Link

While the following issues could be due to a wide array of malfunctioning parts, they could also indicate a blown fusible link.

Battery Issues

The fusible link is part of the battery’s electrical wiring. As such, a blown link could lead to the battery inefficiently charging, affecting the performance of battery-powered parts.

Malfunctioning Power Windows

Power windows can get stuck or become unresponsive due to a blown fusible because they rely on the battery for power.

Don’t put off resolving power window issues. A power window stuck at half open can attract thieves. Meanwhile, one that won’t open would force you to open your door every time you need to pay toll booth attendants, order at drive-thru stations, or just ask someone for directions.

Unresponsive Central Locking System

The central locking system locks and unlocks the vehicle’s doors, liftgate, and luggage compartment. Like the power windows, it’s charged by the battery, which means a bad fusible link could cause the system to malfunction.

Locking system problems are a hassle at least and safety hazards at worst, so address them immediately. For example, the driver’s door getting stuck closed would force you to get in and out using the passenger door, while the luggage compartment failing to lock puts your belongings at risk.

Malfunctioning Wipers

Wipers could develop issues when the battery can’t generate enough voltage to power it due to a blown fusible link.

Wipers are essential when driving under adverse weather conditions. If yours are malfunctioning, determine what’s the cause (whether it’s a bad fusible link or otherwise) and address them right away. You don’t want to get caught in heavy rain with faulty wipers.

Radio Not Working

If your radio is inaudible or flat-out doesn’t work, there’s a chance it’s due to a blown fusible link in the electrical current distribution. A blown link could be what’s affecting the flow of electricity to the radio, resulting in zero power.

A malfunctioning radio isn’t as nerve-wracking or hazardous as the previous symptoms. However, if you rely on it a lot to keep you entertained while you’re behind the wheel, it might be better to get it fixed sooner rather than later.

Dim Lights

The battery might have to bear more load than usual due to a blown fusible link. As a result, it can’t supply the necessary voltage to sustain the usual brightness of your car lights.

It’s dangerous to drive at night with dim headlights because they could limit your view of the road ahead. Likewise, dim brake lights can fail to give the drivers behind you enough warning that you’re braking. Have a mechanic check your lights to confirm whether a bad fusible link is causing the issue.

Illuminated Warning Light

The check engine light could activate when the car computer detects issues with the electrical system, like a bad fusible link.

However, the check engine light could illuminate due to other problems. Scanning for a trouble code would help you narrow down the issue. Stopping by an auto repair shop for a proper diagnosis also works.

How to Check the Fusible Links

If you suspect your vehicle has blown fusible links, check them for damage and issues. The links are usually in a wiring harness near a main harness connection. They’re thinner than the rest of the wires and have a rubbery feel.

Once you’ve located the fusible link, check it for damage. Gently pull on each end of the fusible link. If its insulation stretches, it means the wires have melted and the link needs replacement.

You can also use a voltmeter to determine the fusible link’s available voltage. Check both ends. If one end has voltage while the other has none, the link might be open, which means you need to replace it.

Another way to check if the link is fine is by doing a light test. Attach a test light to the battery’s output terminal and attach the other end to a good ground. If the test light illuminates, it means the link is still functioning.

How to Replace the Fusible Links

Once you’ve confirmed your fusible links are damaged or melted, the next step is to replace them. 

• Step 1: Identify what damaged the fusible link and resolve it. It will prevent the same issue from happening again.
• Step 2: Check the size of the old link and look for a replacement with the same dimensions.
• Step 3: Replace the bad fusible link. Follow the instructions in the service information.