Replacing a blown fuse in your microwave is an easy fix that can get your appliance back up and running. However, microwaves contain high-voltage components, so safety should be your top concern when doing any microwave repair. This comprehensive guide will walk you through the fuse replacement process safely.
Understanding Microwave Fuses
Before you can replace a microwave fuse, you need to understand what a fuse does and why it might blow.
What Does a Fuse Do?
A fuse is a safety device that protects the microwave components from electrical current overloads. It contains a thin wire that will melt if the current exceeds the fuse rating. If there is a power surge or an internal electrical fault, the fuse sacrifices itself rather than allowing excess current to flow. This breaks the circuit and prevents damage or fire. The fuse cuts power to prevent hazards, but it must then be replaced for the microwave to work again.
Common Microwave Fuse Types
There are a few different types of fuses that microwaves may use:
- Glass tube fuses – These cylindrical fuses have wire filaments enclosed in glass tubes with metal end caps. They screw or push into fuse holders.
- Ceramic fuses – Rectangular ceramic fuses have internal metal strips that melt. They may sit in spring-loaded clips or fuse blocks.
- Thermal fuses – Thermal cutoff fuses have two blades connected by a heat-sensitive linkage rather than a melting wire filament. If the temperature gets too high, the linkage breaks the circuit.
Why Would the Fuse Blow?
Common reasons for blown microwave fuses include:
- Power surges
- Electrical faults resulting from age, damage, or wear
- Installing a fuse with an incorrect amperage rating
- A problem with microwave components like the high voltage transformer, capacitor, or magnetron tube
Replacing the fuse may temporarily get your microwave working again. But if an underlying electrical issue caused the fuse to blow, it could continue happening until that problem is corrected.
Testing Fuses
You’ll want a multimeter to test fuses before relying on them to protect your microwave. With the power disconnected, set the multimeter to read resistance or continuity. Touch the fuse’s terminals or blades. An intact fuse will show very low resistance, indicating continuity. A blown fuse will show infinite resistance or no continuity. Always test a new fuse before installing it.
Safety Precautions
Microwaves utilize hazardous voltage that could cause severe electrical shock or death if handled unsafely. Take the following precautions any time you work on a microwave:
Power and Discharge
- Unplug the microwave or switch off the circuit breaker supplying power to it.
- Wait at least 5 minutes before opening any panels to allow voltage stored in capacitors to discharge.
Personal Safety Gear
- Wear rubber-soled shoes and insulated gloves rated for appliance voltage. Remove watches and jewelry.
- Keep your body and tools away from exposed components once panels are off.
- Have another person present to assist in an emergency if needed.
Microwave Positioning
- Place the microwave on a stable surface before working on it.
- Take care not to pinch cables when removing or reattaching panels.
By following these microwave safety procedures, you can check and replace a fuse without risking dangerous shocks. Never take shortcuts when dealing with high voltage appliances.
Locating the Fuse
To replace the fuse, you first need to locate it within your microwave model’s internal circuitry.
Access Panels
The fuse will be housed inside the microwave behind an external panel. Common locations include:
- Fuse cover panel – A separate small panel may cover just the fuse compartment
- Control panel – The panel with the buttons may snap off to access internal parts
- Vent grille – The vent screen can detach to reveal components
- Back panel – The rear wall may have a removable panel
Identify Microwave Model
If you can’t locate an obvious removable panel, consult your owner’s manual or an online diagram for your specific microwave model. This will show the fuse location within your unit.
Locate Mounting Screws
Look closely along panel edges and interior cabinet joints to spot any screws or clips securing panels in place. You may need to remove a few layers, starting with the outer panels and vent grille, before you reach the fuse.
Removing the Old Fuse
Once you locate the fuse holder bracket or block, carefully remove the bad fuse so you can replace it with a fresh one.
Release Mounting Clips or Screws
- Use a screwdriver to detach any mounting hardware securing the fuse assembly.
- Release any locking tabs grasping clip-style fuse holders.
Withdraw Old Fuse
- For cylindrical screw-in fuses, unscrew the bad fuse counterclockwise.
- Slide-in ceramic fuses can pull straight out of their brackets.
- For thermal fuses with spade connectors, detach the wires.
Note Fuse Type and Rating
- Check the amperage rating printed on the fuse body to guide your replacement purchase. Also, note dimensions.
- Ceramic fuses show ratings by the patterns of internal metal strips. Check an online chart.
Test the Old Fuse
Even if the fuse visually looks fine, use a multimeter to check continuity across the fuse. No continuity confirms that thin inner wires have melted through, causing an open circuit.
Buying the Replacement Fuse
With details on the original fuse type, voltage, and amperage, you can select an appropriate replacement fuse.
Match Fuse Type and Dimensions
Choose the same format fuse body that was originally installed – screw-in glass tube, rectangular ceramic block, or thermal cutout. Make sure replacement fuse dimensions match original.
Verify Correct Voltage
Microwave fuses must be high-voltage types rated for 250V or more. Do not substitute cheaper 125V fuses – they lack the proper surge resistance.
Match Amp Rating
Select a new fuse sharing the same amperage as the blown one. Common microwave fuse ratings range from 6A to 30A. Never increase fuse amp capacity.
Purchase Spares
Buy a couple of extra replacement fuses in case the new one also blows shortly. This avoids repeating disassembly just for another fuse.
Stocking up on compatible spare fuses makes it quicker to implement this repair whenever needed down the road.
Installing New Microwave Fuse
Once you obtain the right replacement fuse, carefully insert and secure it on the bracket.
Prep Replacement Fuse
Always perform a continuity test on the new fuse before installation. An open fuse that sneaks through quality control could blow immediately.
Insert New Fuse in Bracket
If the previous fuse was in a screw terminal, twist replacement fuse clockwise until tight. For friction slide mounts, press firmly until it clicks fully into place.
Reconnect Wires
If there are any power wires or connectors, plug them securely onto the new fuse according to the original setup. Verify wires clear any moving or hot components.
Test Fuse Continuity
Before reassembling microwave panels, use a multimeter to confirm intact continuity across new fuse terminals. This ensures it was not damaged during handling and is making positive contact.
Secure Bracket
Refasten any loosened screws or sliding clips to anchor fuse assembly in normal mounted location. This prevents vibration from loosening electrical connections.
Reassembling Microwave
With the working fuse correctly re-installed into the holder, carefully reattach any dislodged panels.
Align All Components
Make sure no wires or hoses get pinched or punctured as you realign chassis parts. Verify any vents or fan openings are unobstructed before next use.
Reattach All Screws
Fasten every original screw snugly without overtightening. Nobody should be able to touch energized components once you power them up again. This includes kids poking things into vents.
Confirm Handle/Door Alignment
If opening the handle or door seems stiff after reassembly, check for out-of-position contact with frame parts. Bindings can damage seals over time.
Reconnect Power
With everything precariously placed back into its original locations, restore power via your breaker panel and plug it into the outlet again. Verify no sparking occurs upon re-energizing.
Operational Test
After allowing a minute for voltages to ramp up, activate a quick heating cycle. Ensure magnetron turns on, blower fan runs, turntable rotates properly, and interior light works. You want to verify all key systems are reconnected correctly before extensive usage.
With a bit of care, nerve, and electrical safety know-how, this relatively easy fix lets you revive an otherwise dead microwave without the cost of replacement. Just be sure to discard any questionable fuses to prevent premature reoccurring failure down the road. Stay safe, but don’t be intimidated to attempt basic household electrical repairs that save money.
Troubleshooting Microwave Issues after Fuse Replacement
While installing a new fuse often resolves microwave operation, it’s possible gremlins still lurk within the appliance electrically or mechanically. If problems emerge after replacing the blown fuse, try this microwave troubleshooting checklist before calling a service company.
Microwave Still Not Powering On
If replacing the fuse yielded no functionality improvement, the issue may lie elsewhere.
- Failed components – If the high voltage capacitor, transformer, or magnetron tube is also faulty, those would still prevent operation after replacing just the fuse. Test the continuity across those parts.
- Control board – The fuse may have blown due to issues on the logic board. Inspect for any burnt spots indicating short circuits. Ensure all wire harnesses connect firmly to boards.
- Door interlocks – Microwaves have safety switches that disable cooking when the door is open. If misaligned, those can prevent powering up. Adjust or replace failed interlock actuators.
- Bad outlet – Verify the outlet itself works, along with any associated GFCI or AFCI breakers supplying the receptacle.
New Fuse Immediately Blows Again
If every new fuse promptly blows when you apply power, there’s an underlying electrical fault plaguing the microwave oven.
- Shorted component – Something like the high voltage capacitor may have an internal short, instantly overloading the fuse. Test capacitance and continuity of individual parts to isolate the failure.
- Line voltage issues – Surging line voltage or inadequate amp service to the building can cause instant fuse failure. Verify your electrical service provides steady 240V to the outlet under load.
- Door not closing – If a switch indicates the door is open, the microwave will not energize to prevent human exposure. Adjust alignment so door correctly presses interlock safety actuators when closed.
Isolating the root cause of persistent fuse failure takes patience and diagnostic diligence before powering up again.
Sparking from Microwave
If you observe electrical arcing or see sparks discharge within the case, promptly power down and correct this dangerous deficiency since microwave leakage can injure nearby humans.
- Wire chafing – Make sure no cables contact the chassis or each other. Tape down or reroute wires so their protective jacketing isn’t worn through over time, shorting conductors.
- Leaking waveguide – Microwave energy shoots through a tunnel between the magnetron and cooking chamber. If its insulation panels develop holes from heat/moisture damage, radiation can arc to the surrounding case
- Faulty door seal – Similar to waveguide leaks, if the door has warped or deteriorated so microwave energy escapes outward during heating, this can arc and spark near the door edges.
Any sparking should be diagnosed and corrected before regularly using a microwave again. Be very cautious of microwave radiation exposure risks.
Preventing Repeat Microwave Fuse Failure
While a blown fuse usually indicates an underlying electrical fault, you can take some measures to enhance fuse longevity proactively.
Install a Surge Protector
Connect the microwave power plug to a surge suppressor. This can absorb transient voltage spikes before they reach the internal electrical system.
Improve Ventilation
Ensure exterior vents aren’t obstructed by items placed on or near the microwave. This avoids heat buildup, which accelerates component degradation leading to short circuits.
Handle Carefully
Since impacts can crack magnatrons allowing current leakage, always move/handle the microwave gently to avoid physical damage.
Keep Exterior Clean
Promptly wipe up any spilled liquids to prevent moisture seepage inside. Accumulated grime also holds moisture against vents.
Check Condition Annually
Do a quick visual inspection of all solder joints, wire harnesses, and components once a year. Look for any signs of overheating or fatigue cracking. Repair observed deficiencies early before they cascade into fuse-blowing failures.
With attentive electrical device care and maintenance, you should encounter less frequent nuisance fuse expiration in your microwave.
Also Read: How to Install and Replace a Microwave
Conclusion
While fuse replacement sounds intimidating for a homeowner, having the right safety gear, testing equipment, and repair knowledge means it’s quite achievable. Pay mind to risks unique to working with high voltage devices, and take your time tracking down any underlying issues triggering repeated fuse failures. Once comfortable working inside electronic equipment, you can rescue many household appliances from the junk heap using basic diagnostic and electrical safety skills coupled with fuse replacements.