Fuses are all through your house. They are the weakest link in the electricity chain and keep electrical surges from damaging appliances and circuits. This Fix-It Guide on fuse replacement tells how a fuse works, what often goes wrong, how to identify a fuse problem, and what parts and tools you will need to test and replace a faulty fuse. It then gives step-by-step instructions for how to test a fuse. (You can order replacement parts at FixItClubParts.com.) Refer to the electrical Service Panel Fix-It Guide for household electrical circuit fuses and circuit breakers.
How Does a Fuse Work?
An appliance fuse is an electrical safety device with a metal strip that melts and interrupts the appliance’s electrical circuit when the circuit is overloaded or the appliance overheats. Electrical fuses protect electrical devices from electrical overloads. Thermal fuses protect them from overheating.
While developing this book we purchased an inexpensive new small appliance but later found out it didn’t work. We tested it and discovered that the thermal fuse was faulty. Rather than return it (75 miles) we replaced the thermal fuse for less than $3.00, and the appliance works fine. Even new appliances can require the Fix-It Club!
Electrical fuses are mounted on the outside of the unit in a screw-out receptacle marked “Fuse,” or inside the unit near the cord and/or a power supply. Thermal fuses typically are installed inside an appliance on or near one of the electrical cord wires. Fuses are clipped, screwed, or soldered into place. Most fuses open a few seconds after a substantial overload begins. Slow-blow fuses are designed to protect equipment where heavy, periodic demands for current would blow a common fuse even though the apparatus is operating normally. Quick-blow fuses open at even a momentary overload; they are used to protect delicate or sensitive components.
What Can Go Wrong with a Fuse?
A fuse can blow, meaning the metal within the fuse casing (usually glass) melts and interrupts the electrical circuit. An appliance or a portion of an appliance will not operate once a fuse has blown. The purpose of a fuse is to stop operation of the appliance or electronic component before the unit is damaged.
Learn to read fuses. A blown fuse that appears smoked or bubbled may indicate a short in the equipment. A clear and otherwise undamaged fuse typically is just worn out and doesn’t point to any other electrical problems in the device.
How Can I Identify a Fuse Problem?
- If an appliance or piece of electronic equipment will not operate, or a portion of it will not operate, you can test the fuse (see below) and replace it if needed.
- If you replace a fuse and the unit still will not work or very quickly blows the fuse again, you will need to check further to find the problem (see the Fix-It Guide for the appropriate item).
What Do I Need for Fuse Replacement?
Many replacement fuses are available from hardware and electronics stores. Special fuses may be available from the manufacturer and aftermarket suppliers. The tools you will need to test and replace fuses include these:
- Multimeter or continuity tester
- Soldering gun and solder
What Are the Steps to Fuse Replacement?
Test a fuse:
- Touch each end of the fuse with a probe of the multimeter set at RX1 (resistance times 1) or with a continuity tester.
- The fuse should show continuity, the passage of electricity through the fuse. Replace a fuse that does not.
- If the appliance or electronic component still does not work, or if the fuse blows again, you will have to look further for the solution. Refer to the appropriate Fix-It Guide.
Never replace a fuse with anything except the type and rating indicated by the device’s manufacturer. Don’t install a 10-amp fuse in a device designed for a 5-amp fuse. Also, don’t install a slow-burn fuse or even a common fuse in a device designed for a quick-blow fuse.