A blown fuse on your motorcycle would be a bad day, especially if you planned on riding.
A weak fuse alone can cause some wavering in your bike’s electrical accessories; it’s no wonder there are so many concerned riders out there asking themselves how to tell if their motorcycle fuse is blown?
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Here’s How to Tell if a Motorcycle Fuse Is Blown:
You can tell if your motorcycle fuse is blown by inspecting the curved metal strip inside the fuse. Switch off both the bike’s motor and ignition, remove the seat, and check your fuses. If the strip is broken, the fuse is blown and will require a replacement, which is usually cheap.
Besides the sure-fire fuse removal and inspection, there are a few ways to know if your bike’s fuse is dead or not.
Hit the kill switch and read on to find out more!
These Are the Signs of a Blown Fuse
The primary sign of a blown a fuse on a motorcycle is a dysfunctional electrical component in the same circuit as the fuse in question. The immediate indication that a motorcycle’s main fuse is blown is the bike won’t start.
- If the fuse on your motorcycle is blown, your bike’s associated electric circuitry won’t work. If you have one specific electronic component that’s not working, start by checking the associated fuse. So, if your headlight fuse is blown, your headlight won’t be illuminated, etc.
- If your instrument gauge isn’t lit up, but your headlight is, they run on different fuses.
- A patchy electronics system is a good sign that one specific fuse is blown.
- If the bike’s battery isn’t charging, a blown fuse could be the culprit.
- If you have blown a fuse on a motorcycle, the circuit that the fuse powers will fail, and the associated functions and accessories will be off. In contrast, the rest of the bike’s electrical parts remain intact.
If your main fuse is blown, your bike will fail to start.
There are too many potential culprits behind a motorcycle that won’t start to go into here; suffice to say that a blown main fuse is high on the list.
The surest sign of a blown motorcycle fuse is if the strip inside the fuse is split or damaged.
You’ll have to pop the seat off and inspect the fuse box to see if the strip inside the fuse of the circuit you’re having issues with is damaged.
We’re planning on sharing some generic instructions on how to inspect the fuse for damage here in a bit, but first things first, there’s no shame in taking your bike to a trusted mechanic for a fuse inspection, as it varies slightly from bike make and model.
Having someone familiar with the electronics of your specific motorcycle inspect the fuse will save some time.
Now here’s how to know for sure if your motorcycle fuse is blown:
- The first step to inspecting the suspect fuse is to flip off your ignition switch and make sure your bike stays off.
- Pop the seat off. There’s usually at least one bolt to remove, but the details vary from moto model to model. Generally, you unscrew a bolt or two, pop the seat up and forward slightly, and then backward.
- Pop open the motorcycle’s fuse box cover. Note: Some bikes require you to uninstall the fuse box, leaving the wiring intact before opening it. Generally, the package is tucked behind the battery. Locate your fuse box, open the cover, and see the various fuses to power your bike’s wiring harness.
- Inspect your fuses by pulling them out one at a time with the unique fuse pulling tool that comes with the toolkit for most motorcycles. If you don’t have yours handy, numerous aftermarket fuse puller tools are available. Pull each one out of the fuse box and look at the metal strip; if the strip is whole, your fuse is alive, but if it’s split or broken, your fuse is blown.
- Replace the blown a fuse with a fuse of the same rating. Some bikes come with extra fuses, usually stashed somewhere around the battery. But in most cases, they leave spare fuse acquiring up to you. Note: If you catch yourself replacing the same fuse repeatedly, you have an issue elsewhere, like a short or a bad ground in the fuse’s circuit.
- Shoot the fuse box cover once you’ve got the lousy fuse diagnosed and replaced. If you had to uninstall it to open it, now’s the time to reinstall the box.
- Put the seat back, moving it back and forth in the opposite motion you used to take it off. Reinstall all the seat bolts and fire up your motorcycle to put her fresh fuse into action.
How Do You Check a Fuse Without Removing It?
You can use a multimeter tool to check a fuse without removing it. A multimeter tests for AC and DC voltage, electrical resistance, and current flow; you can use one to test the current’s continuity and the ohms resistance of a fuse while it’s connected to see if it’s still good.
A multimeter tests a fuse’s circuit resistance via positive and negative leads. The meter leads transmit a small electrical surge from the multimeter’s battery and reads how much of its overflow makes it through the fuse.
A fuse is little more than a wire. While fuses are engineered to prevent electrical damage to your motorcycle’s wiring harness, including electrical fires, they’re also designed to sacrifice themselves to expel power surges from the electronic system.
Fuses aren’t designed to endure that surge forever; in fact, as we’ll explain.
Taking the box out on some motorcycles is more trouble than it’s worth.
Here are 3 ways to test your motorcycle fuses without removing them:
- Multimeter Voltage Test:
- Flip the ignition switch to the on position to get the electrical juices flowing through your bike’s circuits.
- Set your multimeter’s read setting to test for voltage and measure the voltage from the fuse to fuse.
- A fuse is what electricians call a short circuit; therefore, any fuse that reads back with any voltage is blown.
- If they test negative for voltage, the next step is to try the ground contact. If the contacts return a non-zero negative reading across the board, your fuses are all good.
- If both contacts test zero volts to the ground, there’s no power present, meaning you’ll have to energize the circuit or pull the fuse to test it.
- Multimeter Resistance Test:
- For this test, you want to make sure the ignition is off and the battery is disconnected to ensure your circuit isn’t charged; testing the resistance of a charged blown fuse can blow your multimeter.
- After a few minutes with the battery disconnected, your capacitors should no longer be energized. Set the multimeter to test resistance x10.
- Measure across all the fuses. The reading you’re looking for is zero. If there’s any resistance, you likely have a blown fuse in there.
- Testing with a Test Light:
- You want the circuits all charged; make sure your battery is hooked up and flick your ignition switch into the on position.
- Touch each fuses’ ground contact with the test light. If the light lights up, the fuse is good.
- If one ground contact lights and the other doesn’t, then the fuse associated with the unlit contact is likely blown.
- If none of the ground contacts activate your test light, it’s hard to say whether all your fuses are bad or if your circuitry just isn’t charged. You’ll either have to energize the circuitry and retest everything, or you’ll have to remove the fuses and test the more thorough way.
Where Is the Main Fuse on a Motorcycle?
The main fuse of a motorcycle is located in the fuse box, separated from all the other fuses to distinguish it. Most motorcycle fuse boxes are covered in a box, called the fuse box cover, located directly below the seat, near the battery.
The main fuse will be distinguished, sometimes by color, labels, markings, but almost always by location.
The typical motorcycle uses between 6 and 15 fuses, depending on the make, model, style, infotainment packages, LED lights, backlit gauges, and various electronic accessories that come standard on more and more bikes every year.
To help you distinguish the main fuse from the others, we’ve provided a list of the more common motorcycle fuses you might see in the fuse box, along with the remaining fuse besides the main fuse.
Common motorcycle fuses:
- Main Fuse
- Ignition Fuse
- Headlight Fuse
- Hazard Fuse
- ABs Fuse
- Radiator Fan Motor Fuse
- Fuel Injection Fuse
- Backup Fuse
Many motorcycles also come stocked with spare fuses, generally stashed somewhere close to the fuse cover box and the battery.
These fuses are spares you can install on the fly if any of the fuses, as mentioned earlier, blow while you’re out and about.
What Causes the Fuse to Blow?
Excessive electrical current is the most common cause of a blown a fuse. In addition to excess amperage, short circuits, mismatched loading, overloading, and the failure of an electrical component can all blow up a motorcycle fuse.
Incapacitation anywhere in the electrical circuit can damage the fuse associated with the said circuit.
The role of the fuse is to absorb the excess current or surge of electrical failure and blow itself up to remove the power from the faulty system.
- The point of the fuse is to blow in case of an emergency, to protect the battery and electrical system of the motorcycle.
- Fuses are rated for a specific current; the rating is generally depicted with labeling or marking on the fuse.
- If the amperage in the fuses’ circuit exceeds the fuses’ current rating, the fuse will blow.
- Suppose you replace a blown fuse with a fuse rated for a different amperage than the rest of the circuit. In that case, the replacement cannot protect the rest of the course from damage during a failure that results in an overcharge to the system.
For example, if a fuse is rated for 10 Amps, the circuit runs at 10 Amps; if the current charge exceeds 10 amps, the fuse absorbs the excess and blows to shed the power.
- The fuse is set up to blow when the circuit current exceeds 7.5 AMPs. So, as soon as you flip the ignition on and the battery charges the circuit with the 10 Amps it needs, the fuse absorbs everything after 7.5 and blows. Let’s say that happens; the 10 blows, but you only have a fuse rated for 7.5 Amps handy, so you throw it in.
- Now let’s say you replace a 10 Amp fuse with a 20 Amp fuse—if there’s a wire short that causes a 15 Amp overcurrent to surge through your 10 Amp circuit, the 20 Amp fuse won’t absorb the excess, as it’s tuned to start absorbing at 20. The result is that the fuse doesn’t blow when it should, allowing the overcurrent to continue through the circuit, frying the components, and causing long-term electronic damage.
As you can see, fuses are an essential part of a motorcycle’s electrical system’s functionality. Inspecting your fuses is part of routine maintenance.
For more information, please read our article about the common reasons motorcycles keep blowing fuses.