What happens when a fuse blows in a microwave?

Thermal fuses will blow to prevent the microwave from overheating and potentially causing a fire. A fuse will also blow if there is a surge in electricity, which can cause a short circuit.

The average microwave oven lasts about seven years with normal use, and even less with heavy use and poor maintenance. A large family may find themselves replacing their appliance every four to five years as they become more reliant on its use to heat up snacks and leftovers, or to defrost meals.

Fuses are located in many places inside the microwave, including the top, side, and behind the vent grille. Using the wiring diagram can help you locate the appropriate fuse. Once you have located the fuse, remove any necessary wires and fasteners to free it from the microwave.

Microwaves usually contain several types of fuses for safe operation. A main fuse or line fuse is a fuse that will cut the flow of electricity if too much current passes through it. Conversely, a thermal fuse will prevent electrical flow if the fuse is heated to a specific temperature.

The most common cause for a microwave oven not working at all is a blown main fuse. The microwave main fuse will cut the flow of electricity if too much current passes through it.

The most common cause of an overheating magnetron is when too much energy is reflected back into the device. This can happen when you run your microwave empty (something you should never do), or if the turntable has been removed.

If a microwave fuse keeps blowing, it may be because the fuse is not being installed correctly or that the wrong type of fuse is being installed. Microwave parts like door switches or the magnetron, if defective or wrongly installed, will also cause microwave fuses to continuously blow.

Most homeowners spend about $150 to repair or replace the magnetron in a countertop microwave unit. At the low end, you may spend as little as $50 for a minor problem like replacing a fuse. At the high end of the spectrum, you may spend up to $500 on a control board replacement for a built-in microwave unit.

If your microwave is relatively new and the repair costs less than replacing it, the fix is worth it. But are microwaves worth repairing if something major is broken? Probably not. Consider getting a replacement appliance for about $100, which should work for 7 to 10 years.

Remove the fuse from its holder. In some cases you may need a small screwdriver to unscrew the fuse holder cap. Look at the fuse wire. If there is a visible gap in the wire or a dark or metallic smear inside the glass then the fuse is blown and needs to be replaced.