Every circuit in your motorcycle’s electrical system has its fuse—a safety mechanism integrated into an electrical circuit to prevent melting and electrical damage.
The fuse detects excessive charge drawn into the circuit, absorbs the extra energy, and blows itself up to get rid of the current before it fries any of your bike’s components.
Fuses are cheap and easy to replace compared to the components you’d have to replace if they weren’t there to do their job, but what if your motorcycle blows fuses all the time?
Below are the most common reasons why a motorcycle blows fuses and how to prevent them from happening.
1. Short Circuit Ground Out
Whether from corrosion, improper storage, an electrical malfunction, poor upkeep, or just good old-fashioned wear and tear, wire connections break open eventually, grounding out their circuits and blowing a fuse.
It’s typical for wires to crack open on older motorcycles, as your bike’s circuitry heats up and cools down constantly during use, making them brittle over time.
Once brittle, the wires crack open, exposing the copper inside the wires connectors.
If the connector touches anything conductive, like the metal frame, motor, and fuel tank, the stator or battery charge will escape the wire through the exposed copper and ride the metal straight for the earth, hence the phrase short circuit to ground.
A damaged wire creates a short circuit to the ground, which risks damage to the circuit.
Therefore, once the fuse detects the short, it blows to disconnect the circuit before any damage occurs.
If a worn, corroded, or otherwise exposed wire is the reason your fuse blows, replacing the fuse is only a temporary solution, as the short circuit will continue to ground out and blow your new fuses until the worn or damaged wire is replaced.
2. You Replaced the Fuse for the Wrong Circuit
Most modern motos have multiple electrical circuits.
While electrical engineers sometimes wire multiple circuits to the same fuse, most contemporary wiring harnesses equip a different fuse in each circuit.
Therefore, if there’s a short in your starter circuit that blows your starter fuse and you replace your headlight fuse, your starter circuit will still fail.
Check for the wiring harness diagram in the service manual for your make and year model motorcycle. It will show you how many circuits you have and how many run on the same fuses.
Please also read our article about how to tell if a motorcycle fuse is blown.
3. Aftermarkets Electronic Accessories Installed or Wired Incorrectly
Perhaps you or a friend installed some aftermarket speakers, an air ride system, LED lights, a power commander, or maybe you bought your motorcycle used, and the previous owner installed them.
Regardless, if an aftermarket electronic accessory isn’t properly integrated into the rest of your motorcycle’s electronic wiring system, the fuse associated with the circuit the new component is drawing power to or from may blow to prevent damage.
Sometimes, the additional circuitry is more than your battery is equipped for.
In other situations, the accessories are installed by cutting wires and splicing the component into the circuit with electrical tape, exposing the copper and causing a short course.
4. Excessive Draw from Electrical Component
If there’s a problem or lag with a component wired into your bike’s circuitry, the part will draw more power than usual, causing a fuse to blow.
These days, many of your motorcycle’s mechanical parts are electrically powered and governed and timed by the motorcycle’s ECU.
If one of these parts jams or fails, it may pull more power to get through the lag.
If the draw is significant enough, the change in energy course can cause electrical damage.
The fuse associated with the circuit will blow to shed any extra current drawn into the circuit by the struggling component.
For example, if your starter’s drive gear gets stuck, the starter will draw more current from the battery.
If a quick surge is all it takes, the gear may power itself free before any extra current builds up in the circuit.
However, if the gear remains stuck, it will draw more and more current trying to break free. Eventually, an excessive amount of current will be drawn into the circuit, and its fuse will blow to get rid of it before the wires melt or other components in the same circuit fry.
Here are a few components that can have problems resulting in a power draw excessive enough to blow a fuse:
- Fuel Pump
- Fuel injection or timing onboard CPUs
- Ignition Coil
- Display Gauges
- Starter Relay
- Ignition Switch
We’ll get into some of the specifics of some of these in their sections down below.
5. Wrong Fuse Rating
Replacing a blown fuse with a fuse of a different rating than the circuit requires is one of the most common reasons a motorcycle keeps blowing fuses.
Not all fuses are meant to handle the same amperage.
Motorcycle fuses have ratings highlighting how much amperage they’ll permit to enter the circuit before they blow.
The most common motorcycle fuse ratings are:
- 5 Amps
- 10 Amps
- 15 Amps
- 20 Amps
- 30 Amps
Every electrical circuit on your motorcycle exists to bring power from your battery to the various electronically powered components used for operation.
Each of these components needs a certain amount of current to function, and they all have different limits on how much power they can handle before they fry.
For example, your starter and headlights need different amounts of electricity to operate. The fuse installed in their respective circuits is rated to blow before enough power enters the course to overload the component it’s powering.
If the circuit uses a 15 Amp fuse, it will blow once 15 amps of current enter the circuit. If the circuit needs 20 Amps, the fuse will blow before it builds up its usual power.
That said, if a part in the circuit can only 10 Amps of current before it fries, but you install a 20 AMP fuse, the fuse will let up to 10 extra Amps into the circuit before it blows the circuit in jeopardy of overloading.
6. You Need a Circuit Breaker
If your motorcycle’s electrical wiring has been altered or fitted with extra accessories making blown fuses a common occurrence, you may need a circuit breaker to help protect your circuit.
It’s not uncommon for owners of used motorcycles to have trouble sorting through the previous owner’s customized wiring harness fitted with aftermarket parts.
If your motorcycle’s wiring harness is hard to navigate and you can’t figure out why you keep blowing fuses, one solution is to install a circuit breaker.
- A circuit breaker serves the same purpose as a defuse.
- When a circuit breaker detects excess amperage in its circuit, it trips a switch to disconnect the current, the way a fuse blows, protecting the components in the current from overloading.
- The difference between a fuse and a circuit breaker is the fuse has to be replaced after one blowout. A circuit breaker can be reset.
- If there is a severe electrical failure within the circuit, the breaker will click off as soon as your bike fires up, preventing the circuit from ever overloading.
Circuit breakers are rated differently, just like fuses. If you decide to install a circuit breaker on your motorcycle instead of a fuse, buy a breaker with the same rating as the one you’re replacing.
So, if the circuit typically calls for a 15 amp fuse and your fuse blows just a little too often, installing a 15-Amp circuit breaker gives you the option of resetting the circuit and getting back on the road without placing any fuses.
7. Battery Failure
If your motorcycle battery has bad ground or is expired, its erratic behaviors can cause fuses to blow in multiple circuits.
- First, make sure your battery terminals aren’t just loose, as a loose connection can cause starting problems and erratic behavior.
- Next, check the condition of the battery’s terminal cables and connectors. Corrosion or frays in the terminals commonly cause battery failure.
- Inspect the ground cable for many shorts, corrosion, or loose connections.
- Finally, test your battery with a multimeter, following the instructions your multimeter came with to verify that a dead or faulty battery is indeed the reason.
If a faulty battery is the reason your motorcycle keeps blowing fuses, replacing your battery is quick, easy, affordable, and the only fix.
You should also read this article about why a motorcycle won’t start, but the battery is good.
8. Failing Starter Relay
A faulty starter relay will cause motorcycle fuses to blow repeatedly until they are repaired. The dying starter relay draws more power than the circuit to handle attempting to function.
If a faulty starter relay is a reason why your bike keeps blowing fuses, you’ll likely hear a clicking sound while trying to start your motorcycle.
- A motorcycle with a faulty starter relay will often take a few tries.
- You’ll likely hear clicking from your starter; that’s the sound of the relay failing to power the solenoid.
- To power the solenoid, the starter will draw more energy into its circuit than the fuse will allow, and your motorcycle fuse will blow repeatedly.
9. Faulty Ignition Switch
If your ignition switch is worn out or its wiring develops a short, it will attempt to draw extra current into its circuit, causing its fuse to blow.
The ignition switch is typically wired into the starter circuit, meaning that a faulty ignition switch and blow starter fuses continually.
Frayed ignition switch wires need to be replaced, especially if they’re causing shorts in the circuit. Worn or corroded ignition switches need to be replaced, or they will continue to draw excess power and blow your motorcycle’s starter fuses.