This page is dedicated to helping you find and replace a blown fuse, you’ll find a short video outlining how to find, check and replace a blown car fuse, and I also share some mechanics tips together with some helpful tools.
Finding The Fuse Box
Before we can check for a blown fuse we’ll need to find the location of the fuse box, and that can be challenging. Modern vehicles employ a ton of additional electrical accessories. What was once manual function is now electric as standard and that requires more wiring, modules, and of course, fuses, which in turn means more fuse boxes.
Multiple fuse boxes are now common, and they hide everywhere. Under the hood and dashboard, you likely know about, but a few other places you may not be familiar with include under seats, behind kick panel behind the glove box, in the trunk behind trunk side panels, inside the battery box.
Anyhow, my number one mechanics tip for locating the fuse box is – Check the driver’s manual. Common sense you might say, yes but many of us are tempted to search blindly and on modern vehicles, that’s very often a waste of time.
Mechanics Fuse Changing Tips
- Consult your driver’s manual under the “Fuses” section – your driver’s manual is the best source of information. You’ll learn where the fuse lives and what amp fuse to use.
- Important to use the correct fuse type and amp rating – fuse ratings are printed on the fuse plastic body but they are also color-coded.
- Use fuse pulling tool – most vehicles include a fuse pulling tool to aid fuse removal and fitting. The small plastic tweezers-like tool is commonly clipped to the inside of the fuse box cover.
- Many vehicles include a selection of spare fuses inside the fuse box cover for emergencies.
Why Fuses Blow
Fuses don’t usually blow without good reason. Sure it’s a pain in the ass, but on the upside, a blown fuse is better than the alternative – a wiring fire. Besides, swapping out a fuse is easy.
Here’s a few of the most common reasons fuses blow in the first place:
- Incorrect amp fuse – fitting a lower amp fuse to a higher amp rated circuit is a common cause of a blown fuse. Replacing the fuse with the correct amp will solve the issue. The driver’s manual will list the correct rating.
- Faulty external consumer – a blown 12-volt power outlet fuse is a common complaint. Many of us blame the vehicle when in many cases, the problem lies with the consumer being used – faulty pump, phone charger, etc.
- Wiring circuit short – commonly a rubbed through power side wire insulator allows the wire to short on the chassis. The short causes an excessive amp draw which exceeds the fuse amp rating and hopefully, the fuse does its job and blows.
- Faulty component – wiring short within an electrical component such as a motor will cause an excessive draw and blow a fuse.
- Poor accessory wiring – accessories that are poorly fitted (loose uninsulated wiring) are a common cause of blown fuses. As too are accessories powered by scavenged power sources.
Replacement Fuse Keeps Blowing
If a fuse blows immediately after fitting or shortly thereafter, check that you are fitting the correct fuse size. If the fuse is correct, then a deeper investigation will be needed.
Never fit a larger fuse than the rating stated in the driver’s manual, doing so may prevent the fuse from blowing but will damage the wiring circuit and could lead to a fire.
Fitting the wrong fuse size will likely void your vehicle warranty also.
Color-coded fuse chart
Electrical contact cleaner is an auto electrician’s best friend. Fretting or micro corrosion commonly occurs in automotive wiring terminals. And as you know, modules are super sensitive to changes in resistance. Cleaning the terminals is very often all that is required to solve irritating intermittent gremlins. Picture links to Amazon.com.
Fuse Buddy is a useful tool if you’re chasing a battery drain or troubleshooting an intermittent blowing fuse. Remove the fuse and plug in the fuse buddy, operate the circuit, and check the amp draw against the circuit rated spec. A circuit that’s pulling more than the fuse rating will blow the fuse which indicates a short in the wiring or a failing component. Pic links to Amazon.com.
A Power probe is an excellent tool to have around. Great for testing circuits, relays, fuses, checking battery voltage, checking alternator output, checking the ground, volt drop testing. I’ve had a power probe forever and it’s still going strong. Pic links to Amazon.com.
The NOCO genius battery charger is what’s known as a smart charger also known as a battery maintainer or trickle charger. They are smart because they detect the battery state of charge and automatically turn it off and on as needed.
If you’re troubleshooting with the ignition system turned on, it kills the battery, especially higher-end vehicles, to prevent this we use a battery maintainer. Pic links to Amazon.com.
A 250 fuse assortment of standard blade fuses and mini blade fuses from 2 amp to 40 amp, includes a fuse chart and fuse pulling tool. Pic links to Amazon.com.
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.