6 Symptoms of a Blown Alternator Fuse or Fusible Link

A properly functioning alternator is absolutely essential for powering your vehicle’s electrical system and recharging its battery. But if the alternator fuse blows, the charging system fails. Without alternator output, the battery quickly dies leaving you stranded.

Though it seems the alternator itself has failed, a blown fuse could be the real culprit. Read on to learn the symptoms of a bad alternator fuse or fusible link and where it’s located to accurately diagnose and fix this issue.

blown alternator fusible link

See Also: Bad Alternator vs Bad Battery (How to Tell)

Blown Alternator Fuse Symptoms

A blown alternator fuse can cause a host of secondary symptoms, some of which can even be severe enough in scope to leave a motorist stranded along the roadside. Recognizing these potential symptoms is imperative when attempting to remedy the issue at hand in the quickest and most efficient manner possible.

The following are several of the most common symptoms associated with a blown alternator fuse. It won’t be 

#1 – Dead Battery

car battery keeps dying

If you go to start your vehicle, only to find that you are lacking power, a quick check of your alternator’s fusible link is well-advised. A blown fuse will prevent the alternator from charging a vehicle’s battery as designed, thereby leaving it drained of all useful voltage/amperage.

#2 – Strange Electrical Issues

The sudden occurrence of one or more odd electrical issues is yet another sign that an issue exists within your vehicle’s charging circuit. If your battery’s voltage begins to fall from lack of charge, many automotive systems can begin acting erratically.

#3 – Dimming Lights

high beams not working

If you begin to notice that your vehicle’s lights appear dim, this might indicate a charging system malfunction. While a number of issues could be at play, the presence of a blown alternator fuse or fusible link should not be overlooked.

#4 – Low Charge Light

In the event that your vehicle’s instrument cluster begins displaying a “low charge” light, an issue within the vehicle’s alternator circuit would almost certainly be to blame. A quick continuity check of your vehicle’s alternator fuse should be made.

#5 – Burnt, Broken, or Distorted Fuse or Fusible Link

 bad fusible link alternator

In many cases, one can physically verify that an alternator’s fusible link has blown, with a quick inspection. The link itself will look distorted, broken, or burnt. However, if any doubt remains, the status of this fusible link can be verified with the use of a digital multimeter.

By checking for continuity across opposing ends of this link, a blown fuse can be confirmed. A lack of continuity would be indicative of a failure.

#6 – Stalling

In the most severe of cases, a vehicle can actually die while in operation, in the event of a blown alternator fuse. This results when a vehicle’s charging system fails to function, and a battery enters a state of discharge.

When this occurs, it will be as if someone suddenly cycled the affected vehicle’s key to the “off” position.

Fuse vs Fusible Link

fuse vs fusible link

Many well-meaning motorists confuse general-purpose fuses and fusible links. When speaking of an alternator or alternator circuit, most who speak of a fuse are actually speaking of the charging system’s fusible link.

While it is true that most vehicles feature an inline fuse that ultimately powers one or more relays within the charging circuit, in the bulk of cases, a fusible link is also present between the alternator and battery.

The purpose of this specific fusible link is to protect a number of vehicle systems from potentially catastrophic voltage spikes. Without such protection, a spike of this nature could melt wires, burn out intelligent modules, or even start a fire.

Fusible links are designed to burn through and separate, causing an open condition within a particular circuit, thereby preventing further electrical system damage.

By general rule, fusible links tend to be composed of wire that is substantially smaller than that typically found within the circuit that it connects. This effectively creates a weak point, at which controlled wire failure can take place in the event that an overcurrent condition was to manifest.

Before this particular circuit can be successfully re-energized, the blown fusible link must be replaced.

Where is the Alternator Fuse Located?

In most cases, a vehicle’s inline alternator fuse or fusible link will be located between the positive lug of a vehicle’s battery and the positive alternator cable. Alternatively, on some vehicles, this fusible link can be found running between a battery’s positive leads, and the main positive connection on a vehicle’s fuse/junction box.

If your vehicle uses a standard fuse, it will be typically be located in the fuse box in your engine compartment. Because an alternator requires a high amp fuse, the fuse will be larger than your standard blade fuses that are used for smaller electrical components like tail lights.

Related: Can You Jumpstart a Car With a Bad Alternator?

What To Know About Starting Fuse Failure

It is important to remember that a vehicle’s starting fuse does not blow randomly, and without cause. In order for this to occur, a significant voltage spike, or intermittent short to-ground has to have occurred.

For this reason, it is important to diagnose the underlying issue that has caused a vehicle’s alternator fuse to blow. A failure to do so could result in repeated failure.

Internal alternator faults and poor circuit connections can both serve as probable underlying causes of a blown alternator fuse. Under such circumstances, excessive current draw can cause excessive thermal load within the affected circuit, thereby leading the inline fusible link to burn.

Jump-starting of a dead battery is yet another common cause of blown alternator fuses. This most commonly results when an excess draw is placed upon the battery and charging circuits during jump-start, or when jumper cables are inadvertently shorted to a ground source.

Under such circumstances, simply replacing the affected fuse will serve as a viable repair, unless, of course, such aggravating circumstances were to arise again.

Josh Boyd

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