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How a Fuse Works

The primary purpose of an electrical fuse is to help protect a circuit from damage in the event of a short. A fuse is designed to break stopping the voltage flow in the event of a power overload or short circuit. Each vehicle has several fuses that are necessary to safe guard electrical circuits.

Electrical Fuse

Checking Fuses (Always wear protective safety goggles and gloves before work begins)

Electrical fuses protect vulnerable electrical circuits from shorts and burnt wiring. There is basically only one way a fuse can fail and that is, for at least a second there was a short circuit to ground that caused the fuse to blow. Most vehicles fuse panels are located under the hood or under the dash and is labeled with specific amperage ratings and the circuit the fuse protects. Always replace failed fuses with the proper amp fuse; not doing so can result in electrical system damage.

Identify fuses, control relays, micro relays and main fusible links:

Fuse Panel

This is a main electrical junction box; most electrical components are supplied and protected though this box. If an electrical component short circuits it will blow a fuse in this box in most cases. The control relay and micro control relay are used as a high amperage switch for devices that require high amounts of amperage for an extended amount of time. The fuse or fusible link supply voltage to sub electrical systems.

Checking Fuses and Main Fusible Links:

Testing Fuses

There are two ways to check fuses the first is the good old fashion way of removing each fuse and visually inspecting each fuse. It's time consuming but effective. And the easy way, but you need a "test light" before you can begin. Turn the key to the "on" position (do not start), ground your test light lead to a good ground source, like a metal brace under the dash, seat mount bolt or under hood brace. Then lightly touch the service port at the top of the fuse on both sides. If the test light illuminates on both sides of the fuse, the fuse is ok and working properly. If the fuse lights the test light on one side it is blown and needs to be replaced. If a blown fuse is discovered replace the blown it with a new unit. Always replace fuses with the manufactures recommended amperage. If the new fuse blows immediately you have a shorted circuit somewhere in that wiring system. Consult a car repair manual to locate the wiring schematic for your car. Then troubleshoot to system by inspecting the wiring harness and accessories, repair as needed and recheck system.

Common Problems and Solutions

Wrong amperage fuse is installed causing wiring damage
Fuses can cause intermittent short circuit by becoming loose, melted or corroded in the fuse holder. Make sure fuse is held securely and is free of dirt and corrosion

The most common cause of a short tends to be when a piece of wire has a small exposed area that is bare. This piece of bare wire can often rub against metal and create issues for the electrical system because of the sudden surge in electrical current. While there can be numerous causes for a blown fuse, the majority of the causes of a blown fuse tend to be quite simple to repair. Once the failed wire is located the solution usually takes only a few moments to correct. Usually something as simple as repairing a bare wire.

Maintenance

There is very little maintenance that needs to be performed on the fuse system. A visual inspection of the fuses in your car occasionally and replace any necessary. Most fuses are inexpensive costing only a couple of dollars for a pack of five. Looking under the hood on occasions for bare wires can also help. Anything that looks bare, or appears to be losing its insulated coating should be thoroughly taped with electrical tape to help ensure that the wire does not start causing problems with your fuse system or other electrical components. Avoiding proper maintenance on your car, no matter how simple can result in extremely costly repairs.

If further assistance is needed, our certified car repair technicians are ready to answer your car questions.

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