ALT-1 Auto Repairs how to Test a Fuse
Whether it be your vehicle radio, A/C, lights, power windows or some other electrically operated devices, when they don’t work the problem could be as simple as a blown fuse. Yes, you could take it to your local dealer or mechanic, but before you do that, checking the vehicles fuses could fix the problem and save you some big bucks.Locating the Fuse Box(s)First of all, you need to locate the vehicles fuse box(s). Most American made automobiles and light trucks have two, one under the hood, usually located near the fire wall on the drivers side, and a separate one under the dash or built into the drivers side door jam next to the dash. The vehicles owners manual will also have information on the location of the fuse box as well as the types of fuses used.Types of FusesGenerally, all late model vehicles (those built in the last 25 years) use plastic ATM-Mini and ATC-Maxi type fuses. Older vehicles may use the glass or ceramic metal end cap tube type fuses. Both types of fuses use a metal alloy that actually burns “open” when a certain electrical current value is exceeded. ATM-Mini fuses usually come with current values from 5-30 amps and are value color coded; the amperage value is also imprinted on the fuse. The ATC-Maxi fuse type is simply a larger version of the mini type plastic case fuse, having amperage values from 30-100 amps, and are also color coded for easy identification. In the case of glass or ceramic tube fuses, the amperage rating of the fuse is stamped or printed on the metal end caps of the fuse and no color coding is used. Some vehicles also use another type of device called a “fusible link,” but these devices are beyond the scope of this discussion and usually require a trained technician to diagnostically isolate and repair when blown.Detecting an Open FuseOnce the fuse for the non-functioning device has been identified, it can be easily removed with a small tool usually included in the fuse box, or a pair of pliers (a good thing to have under the drivers seat). In the vast majority of cases, determining whether the fuse is blown can be accomplished with a simple visual inspection. If the fuse has burned open the metal alloy fuse link will appear melted and usually, in the case of ATM-Mini or ATC-Maxi fuses it may look a little bit smoky or corroded inside the fuse as well. On rarer occasion, the fuse could actually be blown, but any visual indication of it might be to subtle to detect with the eye.Chances are your not going to have an ohmmeter or continuity light on hand to actually verify whether a fuse is good or bad. If you do, by all means, perform an electrical continuity test to establish the fuses status with certainty. Another way to tell if the fuse is bad, however, is to replace it with another one and see if the associated circuit then works. Most fuse boxes include one or more spares of each type used, but make sure only a fuse with the same color and amperage rating is used to replace the potentially blown fuse. If a lower amperage fuse is used it will likely blow immediately when energized, and if a larger amperage value fuse is used the circuit will be exposed to over current damage. If you don’t have a spare of the right value, borrowing one from some other non-vital circuit is a temporary solution, but a better one would be to have a small kit of spare fuses on hand, again stored under the drivers seat.Beyond the FuseKeeping in mind a fuse is a device designed to protect an electrical circuit from a more catastrophic electrical malfunction, if you replace a fuse and the replace fuse blows right away or within a short time after replacement, some more serious electrical anomaly probably exists in the circuit being protected. Unless you are trained and know what your doing, further analysis is best left in the hands of a professional who is and your going to have to shell out some cash for it. But checking fuses to identify a blown one is something just about anyone can do, and in most cases is all that is required to correct a vehicle electrical problem.
