An alternator that works properly is no doubt vital to your vehicle’s electrical system and to charging the battery. If the alternator fuse blows, however, the charging system is disabled. No alternator output leads to your battery quickly dying and leaves you stranded.
While it may seem the alternator has failed, a blown fuse may be the actual problem. Read on to learn whether it is a bad alternator fuse or fusible link showing symptoms, and where it’s located for diagnosing and fixing it accurately.
Fuse vs Fusible Link
It’s common for well-intentioned drivers to mistake general fuses with fusible links. When most people refer to a fuse when talking about an alternator or an alternator circuit pair are referring to the alternator charging system fusible link.
Indeed, almost every vehicle will use some sort of inline fuse in the charging circuit to ultimately power one or several relays, but in most cases, there is also a fusible link between the alternator and battery.
The purpose of this fusible link is to protect a few vehicle systems from catastrophic voltage spikes to prevent things like melting wires, mission burnout intelligent modules, and ideally, fire.
Fusible links are designed to burn or melt through to produce an open condition, in this instance, preventing further damage to the electrical system
By design, and as a general rule, fusible links are typically made of wire that is considerably smaller than the wire in the circuit they are joining.
This creates essentially a point where controlled failure of the wire can happen in the event of an overcurrent condition.
For this circuit to be energized again after the blown fusible link, you will need to replace the fusible link.
Where is the Alternator Fuse located?
A vehicle’s inline alternator fuse or fusible link will usually be located between the positive lug on the vehicle’s battery and the positive alternator cable.
The fusible link could also be between the positive leads of a battery and the main positive connection on a vehicle’s fuse junction box. If it is a standard fuse, it will usually be in the fuse box in the engine compartment.
Because the alternator has a high amp fuse, the fuse will be larger than a standard blade fuse that is used for smaller electrical components like tail lights.
Blown Alternator Fuse Symptoms
A blown alternator fuse can create a number of secondary symptoms, some of which may be severe enough to leave a motorist stranded on the side of the road.
When attempting to fix a problem in the quickest way possible, it is important to recognize these potential symptoms.
Here are some of the most common symptoms of a blown alternator fuse:
#1. Dead Battery.
If you go to start your vehicle and have no power, it is a good idea to check your alternator’s fusible link.
A blown fuse will prevent the alternator from recharging a vehicle’s battery as intended, and the battery will end up dead with no usable voltage/amperage.
#2. Strange Electrical Issues.
The sudden onset of one or more strange electrical issues is another sign that there is something wrong with the charging circuit of your vehicle.
Once your battery voltage starts to drop due to a lack of charging, many systems can begin to act erratically.
#3. Dimming Lights.
If you notice your vehicle’s lights are dim, particularly the headlights, this could be a sign of a charging system problem. While there are a number of problems that could be causing them to dim, you should not rule out a blown alternator fuse or a fusible link.
#4. Low Charge Light.
If your instrument cluster lights up with a “low charge” light, there is likely a problem in the alternator circuit of your vehicle. A quick check of the alternator fuse in your vehicle would be warranted.
#5. Burnt, Broken, or Distorted Fuse or Fusible Link.
In many cases, you can physically inspect the alternator’s fusible link and see that it has blown. The first impression should tell you it is broken, burnt, or distorted, but if you are in doubt, you can check the condition with a digital multimeter.
By checking for continuity across the opposing end of that link, you can check to see if it is blown. If you do not get continuity, this is a failure.
#6. Stalling.
In extreme cases, if an alternator fuse is blown, a vehicle can die while operating. This would happen if the vehicle’s charging system were inoperative and the battery was discharging.
When this happens, it is as if someone turned the key to the “off” position while driving.
What to Know About Starting Fuse Failure
It should be understood that a vehicle’s starting fuse does not blow randomly, without cause. A significant voltage spike, or intermittent short to ground, has to occur in order to blow a fuse.
It is critical to identify the problem that has caused the vehicle’s alternator fuse to blow, otherwise, it will simply blow again.
Blown alternator fuses can also be caused by internal alternator faults or poor circuit connections.
In these cases, excessive current draw can create excessive thermal load in the affected circuit and cause the inline fusible link to burn.
Jump-starting a dead battery is also a common cause of blown alternator fuses. This is often a result of excessive draw placed on the battery and charging circuits during the jump-start, or if the jumper cables are inadvertently shorted to a ground source.
In these scenarios, simply replacing the blown fuse is a viable repair, that is, of course, unless the aggravating circumstances arise again.