How to Detect and Replace a Blown Fuse

February 27, 2012

Before seeing a mechanic if your car won't start, consider testing for a blown fuse and replacing it. Learn how to locate, check, and replace a car fuse.

Car Fuse Panel Detail Car Fuse Panel

Checking for a blown fuse is one of the first steps to diagnosing a problem with any system on any car. Looking for and replacing a blown fuse on your own can save you a costly trip to the repair shop and it's relatively easy to do. While every car is different, all modern cars use fuses.

What Are Fuses?
Automotive fuses are a very simple way to protect electrical systems. Most modern electronics use fuses of some kind to protect their sensitive circuits. A fuse consists of two terminals and a fuse element encased in a plastic body. The fuse acts as a bridge within a circuit that controls a specific system on the vehicle. If for some reason that system begins to draw more power than it was designed for (due to circuit overload, short circuit or other malfunction) the fuse element begins to heat up, eventually melting and interrupting the circuit.

The Consequences of a Blown Fuse
Although a blown fuse can be a sign of a larger problem with your vehicle, fuses also blow for much simpler reasons. Sometimes drivers overload their vehicle's systems by mistake, for example by playing the stereo very loud or using a certain combination of accessories at the same time. Fuses also age and are more susceptible to blowing over time. If you discover that your car has a blown fuse, replace it with a fuse of the same size and rating. If the fuse continues to blow, it could be a sign of a more serious problem like a short-circuit or a malfunction in one of the vehicle's systems.

Locating Your Car's Fuse Box
Most late model cars actually have two fuse boxes. One is located under the hood and is usually dedicated to the larger systems in the car, like those that govern the engine and transmission. The other fuse box is typically located in the passenger cabin and contains fuses that protect the other systems in the vehicle like lights, entertainment and other accessories. The easiest way to locate your car's fuse box is to consult your car's owner's manual. It should contain a detailed description of the fuse box's location, as well as a description of each fuse and the electrical system it is associated with.

Checking and Replacing Fuses
The first step to checking and replacing a fuse is to locate the fuse associated with the malfunctioning system in the car. Often, there is a diagram of the fuses on the inside of the fuse box cover. If not, you have to consult your owner's manual or an aftermarket manual (such as a Hanes or Chilton's guide) to locate the correct fuse. Once you have located the fuse, remove it by firmly pulling the fuse free of the car's receiving terminals. Some fuses are possible to remove by hand, while others may require a fuse puller (some car's fuse boxes include a fuse puller mounted inside) or pliers to remove. The fuse should be completely clear, with no residue or clouding. You're best off replacing any fuse that is suspect. To replace the fuse, simply push the fuse back into the car's receiving terminals until it is fully inserted.

Replace the bad fuse with a good one of the same amperage. Never install fuses that are a higher amperage than what the fuse panel recommends. This can cause wires to melt, and much more expensive problems in the future than a small plastic fuse. If you replace it with a lower amperage fuse, it might not be enough power to work your electronics. Common fuses include 15 amp, 20 amp and 30 amp.