These 6 Bad Fusible Link Symptoms To Watch For: Testing & Replacement [Explained]

A short circuit or voltage spike can do a lot of damage to your car’s electrical wiring. Fortunately, vehicles have mechanisms to protect the wiring from voltage spikes and short circuits. One way that your car’s wiring is protected from damage is by the use of a fusible link.

Also called a fuseable or fusible link, the link acts as a fuse for your car’s wiring harness and protects the wiring from voltage spikes. So as you might expect, a bad fusible link will leave your car’s wiring vulnerable to damage.

And since that is not something anyone wants, it is essential to know the symptoms of a bad fusible link. These will help you understand when to replace the link and protect your car’s wiring. Below are the main bad fusible link symptoms.

Bad Fusibale Link Symptoms

What is a Fusible Link, and What Does It Do

But before we jump into the symptoms, let’s take some time first to understand fusible links and their role in a car’s wiring system. A fusible link is built to hand a lower amperage than the rest of a car’s wiring. 

Therefore, when there is a short circuit or a voltage overload, it is the first failure point. The link melts as it has a lower heat resistance than the wiring harness it is protecting. When the link melts, it cuts off power to the rest of the wiring system. 

While they function like fuses in a circuit, they are not fuses. Instead, fusible links are typically wires that come in varying thicknesses, usually measured in gauges. The gauge of these wires is often abbreviated as AWG in reference to American Wire Guge. 

The lower the gauge number, the thicker the wire. The wires are usually covered in a fireproof covering and are generally thinner than the wiring harnesses they are connected to. The fireproof covering protects the engine bay from fire damage.

Where do I find the fusible link in my car?

So where can you find a fusible link in your car? Typically these fusible links will be found between delicate harnesses and large sources of power. Therefore, you can expect to find a fusible link between the battery and the alternator.

The battery fusible link is designed to transmit high electrical currents while being able to protect the car’s wiring harness. 

Fusible links amperage color codes

Like fuses, fusible links come in different colors to indicate their amperage rating. The colors used may vary from vehicle to vehicle. But the most common colors are blue, green, red, orange, black, and brown.

Red fusible links will have an amperage rating of about 20 amps, green will be 16 amps, yellow is 23 amps, black is 26 amps, brown is 33 amps, and blue is 35 amps. 

How many amps can a 12 gauge fusible link handle?

A 12 gauge fusible link wire can handle about 41 amps of amperage. However, the rating can be higher to about 45 amps in some car models. 

Top 6 bad fusible link symptoms

How do I know if my fusible link is blown? Fusible link symptoms can be challenging to identify since they can be similar to other electrical problems. However, blown fusible link symptoms can still be identified.

Here are some common signs of a blown fusible link.

Power windows not working.

The battery powers your car’s power windows. If the fusible link is blown, it may manifest in problems with the power windows. This will make it difficult to close or open the windows automatically. 

It is worth noting that this problem can also result from battery problems or a bad alternator. When the car is running, it draws power from the alternator. And if it fails, it places more load on the battery, resulting in problems.

Nonetheless, if you have problems using your power windows, it may be an issue of a blown link. Therefore, it is wise to check before resorting to buying a new alternator or battery. 

Central locking and wipers not working

Like power windows, the central locking system and wipes draw power from the battery and alternator. Therefore, a blown fusible link can cause these components not to work efficiently. But, again, it may be caused by alternator problems or battery problems as well. 

So checking that your alternator and battery are working correctly is important before blaming the issue on a blown fusible link. 

Radio not working

Another electrical component that can be affected by a blown fusible link is the radio. Thus if you notice the radio isn’t working, the cause may be a blown fusible link. 

Battery failure

Since the fusible link is part of the electrical wiring from the battery, when it’s blown, it can lead to the battery not working correctly. This will result in the battery being incapable of charging efficiently and can result in other issues. Notably, you can have problems starting.

Dim lights

When your car is running, it uses power from the alternator but needs power from the battery to start. This is why headlights dim when you switch on the ignition key. Also, if you have a blown fusible link, it may lead to the battery bearing more load than usual.

Dim headlights will manifest this. Thus if your headlights are dim, it may be a blown fusible link. 

Warning lights on and bouncing speedometer needle

A blown fusible link will light warning signs in the car. So if you notice your check engine light is on, the cause may be a blown fusible link. A faulty fusible link will also shake the speedometer needle when you turn on the ignition key. 

How to test the fusible link

The symptoms outlined above can also result from a bad alternator or a faulty battery connection. So it is important to verify that the fusible link is the problem before replacing it. The best way to test a fusible link is with a multimeter.

First, check the negative battery plug. Place the black outlet of the multimeter on the negative battery terminal and the red outlet anywhere on the vehicle body. You should get a reading on the multimeter. This shows the battery is fine and the battery plugs as well.

Next, take the multimeter and test the alternator cable. If you get reading, it means the alternator is functioning fine as well. This leaves the fusible link. So how to test fusible link with a multimeter? Use a multimeter and place the red inspection rod on the fusible link.

The fusible link will be thinner than the rest of the wires and have a rubbery feel, and in most cases, it will have the words fusible links on it. Check this wire for physical damage. A blown fusible link will cause noticeable physical damage. 

Another way you can test the fusible link is by wiggling it a bit while the key is in the ignition. If it is the problem, you will notice that the speedometer will stop bouncing when you do this. 

How to replace a fusible link

When replacing the fusible link, make sure you use a replacement link of the same thickness as the one you are removing or on slightly higher; also, before replacing, disconnect the negative terminal of the battery first. 

Next, cut the plastic strip where the fusible link connects to the thicker electrical wires. You should see the wire connection that connects the fusible link to the wiring. Use a pair of pliers to cut the fusible link from the wire connection. 

Cut the fusible link on the other side to remove it. Then take the new fusible link and blend its wires together with the wiring you are attaching it to. Then twist the wires around each other to mix them to form a uniform joint. 

Attach a small crimp on the wire connection. Use a heavy-duty soldering iron to solder the wire joint. Place the soldering iron below the joint. For this job, use a lead solder as it has a lower melting point. 

Next to us is a heat shrink tubing to cover the joint you have soldered and ensure the tubing covers the entire joint and overlaps each of the wires. This is done to make the joint watertight. 

How costly is it to replace fusible links?

Replacing a fusible link is typically not costly. Fusible links are cheap and cost about $3. The process of replacing the fusible link is also not complex and is something you can do.

How often should I inspect and replace fusible links

Typically it is advisable to replace the fusible links in your car at least once a year. For inspection, you need to inspect the fusible links during general maintenance. It is also wise to inspect fusible links if you encounter the symptoms highlighted above. 

Frequently Asked Questions

How Long Are The Fusible Links?

Fusible links typically measure 9 inches long or shorter and should be longer than this.

Would a blown fusible link let you start your car?

In most cases, if your fusible link is faulty, your car will not start. This is because the fusible links are important in delivering the electrical power needed for ignition. So if this power is not delivered correctly, the vehicle will not start.

Can you replace a fusible link with a regular fuse?

It will be difficult because fusible links are wires with fireproof insulation covering, while fuses are plastic components used in circuits. Also, fusible links can handle a lot of currents before they blow, and only mega fuses can handle the same kind of current. So using mega fuses in place of fusible links simply isn’t practical.

How do you choose the size of the fusible link to use?

The thickness of the fusible link will depend on the thickness of the wire you want to use it on. Ideally, the fusible link should be at least four gauges smaller. For example, an 18 gauge link can be used on a 14 gauge wire. 

Conclusion

Diagnosing bad fusible link symptoms can be challenging, given the symptoms of a bad fusible link can be a result of other issues. Therefore, if you detect any of the symptoms above, check the alternator and battery terminals to verify that the problem is indeed a blown link.

Last Updated on May 16, 2022 by Rifen

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