Is your radio cutting out, headlights dimming, or power windows refusing to budge?
Chances are you might have a blown car fuse.
A fuse is like your car’s electrical bodyguard — designed to break the circuit and protect the system when things get overloaded.
So, the best thing to do is to swap out a bad fuse ASAP.
But first, we’ll explain how to tell if a car fuse is blown so you can tackle it right away. We’ll also explore why a fuse blows and share some clever tips to keep it from happening again.
This Article Contains:
- How to Tell if a Car Fuse Is Blown: 5 Key Signs
- What Causes a Car Fuse to Blow?
- How to Diagnose a Blown Fuse
- How to Replace a Blown Fuse: A General Know-How
- How to Stop a Fuse from Blowing: 5 Simple Tips
How to Tell if a Car Fuse Is Blown: 5 Key Signs
Luxury brands like Mercedes-Benz and BMW use a circuit breaker for systems that need frequent or consistent high power, such as power windows and sunroofs. Unlike a single-use fuse, circuit breaker is a resettable device that automatically restores power once an overload is resolved.
But if your car relies on multiple fuses instead of a circuit breaker, here are some tell-tale signs of a blown one:
1. Electrical Components Not Working
Each fuse is built to protect a specific electrical system by breaking the circuit when excessive current flows through it. This shields the electrical wiring and components from potential damage.
So when a fuse blows, the electrical device it safeguards, like lights, radios, or power windows, will stop working until you swap in a fresh fuse and bring it back to life!
2. Clicking Sounds
The clicking you hear is often from a relay. A relay is an electrically operated switch that controls the current flow in an electric circuit.
A blown car fuse disrupts the flow of electricity in a circuit and makes the relay lose and regain power repeatedly. As a result, the relay rapidly switches on and off, resulting in the clicking noise.
3. Flickering Lights
Dimming or flickering lights indicate an overloaded electrical circuit, which can cause a bad fuse. This flickering happens when the electrical flow becomes unstable right before the fuse breaks.
NOTE: A bad battery or alternator issue can also result in flickering lights.
4. Accessories Not Working
Each accessory in a vehicle operates on its own circuit, protected by a fuse. So if external accessories like the cigarette lighter, GPS, or phone charger stops functioning, it’s a common sign of a blown fuse for that particular circuit.
Additionally, if multiple accessories stop working simultaneously, it could indicate a problem with the fuse box or electrical wiring rather than just a single blown fuse.
5. Visual Inspection
To check if a fuse has blown, remove it and inspect it closely. Here are some observations that can point to a blown fuse:
- Broken thin wire inside the fuse
- Signs of melting on the fuse or its outer casing
- Dark burn marks on the fuse or its outer casing
NOTE: If your fuses blow frequently, multiple components stop working, or you get a burning smell, it can indicate a more serious electrical problem, like a short circuit. In such cases, it’s best to seek expert help.
But why does your fuse blow?
Let’s find out.
What Causes a Car Fuse to Blow?
Here are some reasons why your fuse blows:
- Overloaded circuit due to plugging too many devices into one outlet
- Short circuits caused by damaged wires or faulty electrical components
- Aged or corroded fuses
- Using incorrect fuse rating
- Faulty components, like a motor or light, draw more current
If your fuse doesn’t show any of these physical signs of damage, you’ll need a test to confirm if it has officially bit the dust.
How to Diagnose a Blown Fuse
Since diagnosing and replacing a blown fuse involves dealing with electrical components, it’s best to leave it to a seasoned professional.
The mechanic will typically use a multimeter to check your car’s fuse. They’ll place the two probes of the multimeter on the fuse’s exposed metal pins while it’s still in place — one on each side. The black probe will be connected to the negative side (ground) and the red probe to the positive.
If the reading is low (close to 0 ohms), you have a good fuse. But if it’s high (indicating an open circuit), it’s blown.
Alternatively, the mechanic may also use a test light. If the light illuminates on both ends of the fuse, it’s in good condition. However, if the light fails to illuminate on one side of the fuse, it’s blown.
NOTE: Although it’s not necessary, disconnecting the battery before testing the fuse helps prevent risks of electric shock or damage to electrical components.
Wondering how a new fuse is installed?
Let’s settle your curiosity.
How to Replace a Blown Fuse: A General Know-How
Here’s how a mechanic will swap out a car fuse:
- Ensure the vehicle is parked and disconnect the battery to prevent any chance of electrical fire and other accidents.
- Locate your vehicle’s fuse box, which is typically found under the dashboard or in the engine bay.
- Remove the fuse box cover and use the fuse diagram inside the cover or in your vehicle’s owner’s manual to locate the fuse associated with the faulty component.
- Use a fuse puller or a pair of pliers to remove the blown fuse from its slot gently. Look for a broken wire or burnt interior to confirm you have a faulty fuse.
- Install a new fuse of the same amperage rating, type, and voltage. An automotive fuse generally comes in three types: blade fuse, cylindrical glass fuse, and cylindrical plastic fuse.
- Finally, turn your vehicle on and test if all components work properly.
But you don’t have to go through these troubles if you follow some maintenance tips.
How to Stop a Fuse from Blowing: 5 Simple Tips
Here are some preventive measures you can follow to extend the life of your automotive fuse:
- Regularly check and replace aging fuses: It’s often recommended to change your fuses every 10 years to ensure optimal performance and prevent a potential electrical issue.
- Use the correct fuse: A new fuse with a different rating than the previous one can damage the electrical component it’s meant to protect.
- Inspect the electrical system: Regularly inspect every wire, like a fuse wire, and electrical component for damage or wear.
- Install surge protectors: For vehicles with sensitive electronics, surge protectors can prevent voltage spikes.
- Park in shade: Park in cooler spots during hot weather to protect your car’s electrical components from overheating.
Get Your Car’s Fuse Fixed with AutoNation Mobile Mechanic
A simple fuse replacement today could save you from expensive repairs tomorrow. Ignoring it can lead to electrical shorts, malfunctioning systems, or even more serious electrical failures.
Need a pro to handle it?
Let the seasoned professionals at AutoNation Mobile Service take care of it for you!
We’re a mobile auto repair and maintenance service available seven days a week. We also offer a 12-month, 12,000-mile warranty on all services like brake repair and engine repair.
Contact us to get your faulty fuse fixed right from your driveway.