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What Causes a Blown Car Fuse?
There are a handful of different fuse styles that are commonly used in cars today, particularly blade fuses in standard, mini, and maxi sizes. There may also be glass fuses in older vehicles, larger high-amperage fuses, as well as fusible links and other lesser-used styles. Regardless of the type of fuse, the cause of a blown fuse is almost always from something on the circuit demanding more power than the fuse is rated for.
For example, a worn power window motor might need more energy to move the window glass up, or a chafed wire is grounding out on a sharp edge, closing an electrical loop with a higher current than the circuit should have. Like a light bulb, the filament in the fuse heats up and burns through. When that happens, the circuit is completely disconnected from the power source, often saving it from damage.
Fuses can blow or break in other less common ways like a jarring impact, but it’s far more likely your blown fuse is related to an electrical fault.
Symptoms of a Blown Car Fuse
The most likely blown car fuse symptoms are related to electrical functions not working at all. That’s almost always one specific system affected, with acute signs like:
- Power door locks not cycling
- One or more power windows not going up or down
- Heater fan not working
- Power outlets not functioning
- The radio quits working or lighting up
- The windshield wipers won’t work at all
- Headlights, taillights, or other lighting systems aren’t functioning
Occasionally, you might detect a slight burning odor when the fuse first blows, and some vehicles might even have a dashboard warning of “CHECK FUSES”. Once a fuse blows, the affected systems will not operate at all until the fuse is replaced, but an electrical diagnosis should be done to ensure the problem doesn’t persist.
How to Identify a Blown Car Fuse
Generally, there are three ways to identify a blown car fuse:
- Perform a visual check. Most common fuses are transparent and you can see the filament running through it. The filament must be continuous from one terminal to the other for current to flow. If the filament is broken through, there’s melting visible, or there are black or brown burn marks inside or on the outer portion of the fuse, it’s an indication the fuse is blown.
- Use a circuit tester/test light or DVOM. These pieces of diagnostic equipment are fairly simple to use and can indicate if there’s continuity from one side of the fuse to the other.
- Replace with a known good fuse. Another easy way to determine if a fuse is the culprit for a problem is to replace it and test if the system begins working again.
Checking for a bad fuse is one of the less complicated tests you can perform on your car. However, simply replacing the fuse might not be all that’s required. If the fuse blows again, especially if it happens immediately, there’s another problem that needs to be diagnosed and corrected on that circuit.
Tips for Replacing a Blown Car Fuse
Changing a fuse isn’t rocket science, but doing it right is necessary or it could damage the new fuse or the wiring or parts on that circuit. Here are a few tips to keep in mind:
- Always replace the fuse with the exact same fuse rating as the original. Most cars have a diagram on the fuse panel lid with the fuse rating listed. Using an oversized fuse rating can result in permanent damage to electrical components or burnt wiring.
- Use the fuse puller in the fuse compartment (if equipped). It’s the easiest and safest way to pull a fuse without cracking it. A pair of needlenose pliers can also be helpful if they’re used gently.
- If the fuse sparks and burns out immediately on installation, it indicates an issue like a short to ground that needs to be fixed.
When you need new fuses for your vehicle, find them at your local AutoZone. Get the exact fuse rating, size, and style you need in a few clicks. Need a little help? Our associates can lend a hand to ensure you get what you’re looking for. If the job is too big for you, seek out one of our Preferred Shops to help you do the job.
FAQ/People Also Ask
How do I know if my car fuse is blown?
You can perform a visual check to see if there’s signs of burning or if the filament is intact or not. Or, use a circuit tester to verify if there’s continuity between the two ends of a fuse.
What happens if a fuse blows in your car?
When a fuse blows, the electrical functions that are powered by that circuit will stop working completely.
Will your car start with a blown fuse?
It depends. If the fuse is for a system unrelated to the ignition, starter, or battery, your car will likely start and run.
Is it bad to drive with a blown fuse?
It might be. If the blown fuse is for a system that’s to help with vehicle safety, it can be unsafe to drive until the problem is rectified.
What happens before a fuse blows?
Before a fuse blows, you might notice minor symptoms like flicking lights, an indicator, a light burning smell, or buzzing and clicking sounds. It varies according to what the circuit is intended for.
