Fusible Link vs. Fuse: A Comparison Between Two Safety Points in Automotive Electronics

We’ll compare fusible link vs. fuse in this article. 

Although built using rigorously tested cables and harnesses, automotive wiring systems are not immune to electrical faults. 

Sudden surges or shorts can affect critical sensors, damage components, or even cause significant shorting in other areas that can start fires. 

So the system needs safety points. And the two critical ones are fusible links and fuses. Let’s compare fusible links vs. fuses to see how they function and differ.

What Are Fusible Links?

In general, fusible links are mechanical or electrical safety devices. 

The former comprises two metal strips soldered using a fusible alloy that melts at specific temperatures. 

So when the heat levels increase, the alloy separates the two pieces, creating a separation (discontinuity).

Here, we are more interested in the electrical fusible link because it is typical in automotive applications. 

It consists of a short piece of low-voltage insulated cable that is usually 2-4 AWG wire sizes thinner than the cables it connects. 

For instance, you can use a 12 AWG fusible link to protect an 8 AWG wiring line.

The purpose of this thin wire is to be the sacrificial lamb in case of an electrical fault, overload, or short circuit. 

Since it cannot handle the excess current, the wire will burn out, cutting electric current flow and preventing further disaster.

And if the wire heats to its melting point, the hot wire can be disastrous because it can ignite the insulation around it.

 So fusible links must have special material insulation that can withstand high temperatures. 

This fire-resistant insulation usually feels more rubbery than materials in other cables.

How To Locate Fusible Links

Cars and trucks have several fusible links, and they usually protect high-amperage circuit lines, such as from the battery to the starter motor. 

You can also find them near the alternator and battery in the engine bay.

Wires evacuating power from a car’s alternator

If the fusible link between the battery and starter motor burns, the vehicle can’t start because power won’t reach the starter.

 It might be inconvenient, but the link will protect your car from fires or other far-damaging electrical issues.

So if the wire burns, the first thing you need to do is locate it. 

As stated earlier, one way of identifying this link is through its rubbery insulation feel.

 And it should be short. Most have “fusible link” tags, so you don’t have to struggle to find them.

But the tag might be absent in older vehicles.

 So look for tiny wires near the battery or firewall, which are thinner than the wiring harnesses connecting them. 

In newer cars, look for these wires in the fuse box.

A car’s fuse box

What Are Fuses?

Fuses operate like fusible links. 

They have a thin wire that heats and melts to create discontinuity if there is a surge or electrical short. 

But fuses typically handle less current. 

So while fusible links safeguard high electrical current sources and parts or delicate harnesses, fuses handle regular car components.

Car Fuse Generations

Car fuses began as glass tubes with metal-capped end terminals and thin metal strips inside the cylinder connecting the metal ends.

Glass tube fuses

Bosch fuses had the same cylindrical shape but replaced the glass tube with solid ceramic and an external metal strip.

Ceramic fuses

Blade fuses emerged in the mid-70s with types like ATO and ATC.

 They are still the mainstream fuse types used in modern cars because they are tinier, more durable, and lighter than glass fuses.

Additionally, they require half the parts and have a simple structure that is easier to mass-produce than their cylindrical counterparts.

Types of Automotive Blade Fuses

Blade fuses differ on factors like the number of terminals and size, with the large ones handling higher amounts of current. 

And they can have translucent or transparent housings, both being easier to diagnose because you can see the wire inside.

Blade-type car fuses

But the size differences are more significant and include the following.

Maxi Fuses (APX)

These are the most sizable and highest amperage blade fuses, making them ideal for handling high-current consumption components.

Regular Blade Fuses (ATO, ATC, APR, and ATS)

These are the most typical fuses in modern vehicles, especially the ATC type. 

They are broader than their height but with slight structural differences among them. 

For instance, the ATOs have an open bottom, while ATCs have an enclosed plastic body.

Mini

Some manufacturers began replacing ATCs with mini blade fuses, but they are still not as common as the regular size. 

These fuses come in various amperage ranges and are available in low-profile versions.

Mini blade fuses

Mini fuses have the same width and height dimensions, but the low-profile versions are shorter because their blade terminals barely extend past the plastic body.

Micro

Micro fuses come in two types. Micro2 are the tiniest blade fuses and have lengthier heights than their widths. 

Micro3 fuses are more sizable than the Micro2 type but have a lower profile and contain three terminals. 

Three terminals imply they have two metal strips inside that can handle two circuits concurrently.

Automotive Blade Fuse Color Coding

Although blade fuse sizes directly relate to their current ratings, they don’t have the same rating per size. 

For instance, not all micro fuses have the same electrical current rating. 

So manufacturers use color codes to ensure precise electrical rating matching when replacing damaged fuses.

Here is a color code chart you can use for guidance.

Color	Current (Amps)	Maxi	Regular	Mini	Micro
Dark Blue	0.5	No	Yes	No	No
Black	1	No	Yes	No	No
Gray	2	No	Yes	Yes	No
Violet	3	No	Yes	Yes	No
Pink	4	No	Yes	Yes	No
Tan	5	No	Yes	Yes	Yes
Brown	7.5	No	Yes	Yes	Yes
Red	10	No	Yes	Yes	Yes
Blue	15	No	Yes	Yes	Yes
Yellow	20	Yes	Yes	Yes	Yes
Clear	25	Gray	Yes	Yes	Yes
Green	30	Yes	Yes	Yes	Yes
Blue-Green	35	Brown	Yes	Yes	Yes
Orange	40	Yes	Yes	Yes	No
Red	50	Yes	No	No	No
Blue	60	Yes	No	No	No
Amber/Tan	70	Yes	No	No	No
Clear	80	Yes	No	No	No
Violet	100	Yes	No	No	No
Purple	120	Yes	No	No	No

The color coding is standard except for the 25A and 30A maxi blade fuses (gray and brown, respectively).

A brown 7.5-amp, 32V blade fuse

Besides color, you can tell a fuse’s amp rating by checking the details engraved in the plastic case. 

And you can check the vehicle’s fuse diagram to determine the correct fuse size to plug into the respective slot.

Fusible Link vs. Fuse: Construction

Fusible links have a more sophisticated construction and are longer than fuses. 

They consist of short wires encased in fire retardant insulations that withstand high temperatures. This design makes them costlier than fuses.

Fusible Link vs. Fuse: Replacement

Fuses are easy to replace because they have blade terminals. You can pluck the blown fuse, then push a new one into the slot.

 The process does not require tools. Also, you can tell if the fuse is kaput by visually checking the metal strip inside because the plastic cases are usually transparent or translucent.

An electrician checking car fuses

But detecting faulty fusible links is more difficult because they have opaque insulators. 

You need a multimeter to test for continuity or resistance between the positive battery terminal and the fusible link end.

If faulty, disconnect the battery, replace the damaged link, then re-attach the battery. This process will require some tools.

Wrap Up

Fusible links and fuses are essential electrical circuit protection features in vehicles, and both must be present because they have different functions. 

So you cannot replace a fusible link with a fuse or vice versa. That’s it for this article. Comment below to share your thoughts and keep the conversation going.