A blown fuse is one of the most common reasons for a malfunctioning microwave. Replacing the fuse is an essential repair that can easily be done at home with some basic tools and safety precautions. This step-by-step guide will teach you how to locate, test, and replace a blown microwave fuse to get your appliance back up and running.
Understanding Microwave Fuses
Fuses are safety devices designed to protect electrical circuits and appliances from power surges or internal faults. Here’s a quick overview of how they work:
- Fuses contain a thin wire that melts and breaks if the current flowing through it exceeds the fuse rating. This stops the flow of excess current and protects the microwave components.
- They are connected in series along the power supply line inside the appliance.
- Common fuse ratings in microwaves range from 10 amps to 30 amps. This information should be printed directly on the fuse.
When a microwave fuse blows, it cuts power to the unit, rendering it inoperable. Fuses don’t repair themselves, so when this happens, it’s important to diagnose the underlying issue and install a new fuse with the matching amperage rating.
Why Do Microwave Fuses Blow?
Microwave fuses are designed to blow under abnormal electrical conditions to prevent damage. Here are some of the most common reasons why a microwave fuse may blow:
- Power surges – A large spike in voltage can overwhelm the fuse. This can happen during storms.
- Faulty components – An internal short circuit or failing component like the high voltage diode or transformer can draw excess current and blow the fuse.
- Loose wiring – If wires have loosened over time, it may create arcing or shorts inside the appliance that overload the circuits.
- Old age – Fuses can weaken over years of normal usage until excess current makes them blow.
If your fuse was blown due to faulty wiring or a component failure, it’s possible that it may blow again unless that underlying problem is repaired. Always have a service technician evaluate the microwave if there’s no obvious reason for repeated blown fuses.
Microwave Fuse Replacement Safety
Replacing electrical components in appliances carries some safety risks. Here are important safety guidelines to follow throughout the fuse replacement process:
Unplug the Appliance and Disconnect the Power
- The very first step is to unplug the microwave to disconnect powerfully.
- Do not rely solely on turning off a switch or breaker. Pull the plug.
- This protects against electric shock while you work inside the unit.
Allow Components to Discharge
- There may be capacitors in the microwave circuitry that store dangerous levels of electricity even when it’s unplugged.
- Let the appliance sit undisturbed for 5 minutes so these components can discharge fully. This dissipates stored electricity.
- Set a timer because the discharge process is invisible.
Use Insulated Tools
- Any tools you insert into the interior of a microwave should be fully insulated to prevent accidental electric shocks or shorts. Use insulated screwdrivers and pliers.
- Do not insert metal silverware or wear rings which could make inadvertent contact.
Check for Power Before Reconnecting
- Before plugging back in the repaired microwave, verify the outlet is working correctly using a multimeter or voltage tester.
- Once you reconnect power, confirm microwave operation immediately while being cautious of live circuits.
Following these electrical safety guidelines is extremely important before taking apart a microwave to test or replace fuses inside. Now we’re ready to locate the fuse.
Locating the Fuse Inside Microwaves
Microwave fuse locations can vary across different appliance makes and models. However, in most mid-sized household microwaves, you should find the fuse behind a removable maintenance cover on the outer housing. Here are the basic steps to locate this fuse panel:
- Unplug your microwave and open its door. Inspect the outer housing walls, ceiling, and floor. You should see one removable panel secured by screws. This provides internal access.
- Carefully note what type of screwdriver is needed to remove those screws before proceeding. Often standard Phillips-head or slot screws are used.
- Unscrew the panel slowly and set it aside in a safe place. Inside there will be a circuit board attached to a panel or mounting bracket. The main fuse will be clipped to this.
If you don’t immediately see an obvious fuse, trace along the white or black power wires coming into the unit’s chassis to find where they connect. Near this wire, termination is often where you’ll spot a cylindrical fuse body and metal end caps.
Having trouble finding the fuse? Many microwave ovens place them in different locations, which require partially disassembling the case. Check your model’s official diagram before proceeding. If you cannot confidently access the fuse compartment, contact an appliance service technician to have them safely locate and replace it.
Testing the Microwave Fuse
Before installing any replacement fuse, first test the suspected blown fuse for continuity using a multimeter. Follow these steps:
- Set your multimeter to test resistance/continuity.
- Touch the meter probes to the metal end caps on each side of the fuse.
- Check for a reading near 0 ohms resistance if contacts are good.
- If you get no tone or see OL (open line) on the screen, there is no continuity meaning the fuse has blown.
This fuse continuity check confirms whether or not the existing fuse needs to actually be replaced. Never skip testing the old fuse – otherwise, you risk another new fuse blowing immediately if the underlying problem is not resolved.
It’s also possible to have a blown microwave fuse that looks visually fine. Testing verifies if the thin metal strip inside has melted through despite appearances.
Choosing a Replacement Fuse
Microwave fuses need to be replaced with the exact same fuse style, dimensions, and amp rating as the original. There should be markings on the fuse detailing its electrical specifications. If you cannot read any markings, pull up the owner’s manual supplied with your appliance. This should state the fuse ratings needed.
Things to look for when buying a replacement microwave fuse:
- Type/style – Common types are glass tubes or ceramic body fuses with metal end caps. Choose the matching style.
- Voltage – Typically 125V or 250V fuses. Voltages must match.
- Amperage/amp rating – Select a fuse with identical amps as the blown one (usually 10, 15, or 20 amps). This regulates current flow.
- Size – Pay attention to dimensions so the replacement properly fits the fuse clips.
- Fast acting – Microwave fuses should blow quickly during overload, marked fast acting. Avoid slow blow types.
- Standards – Look for fuses certified to safety standards like UL or CSA.
Many appliance parts vendors online carry microwave fuse assortments you can conveniently order with same-day shipping. Bring your blown fuse into the store for an accurate in-person match. Only install replacement fuses that are identical for optimal safety and performance.
Step-By-Step Microwave Fuse Replacement
Once you have located the blown fuse, conducted continuity tests to confirm it’s faulty, and purchased the correctly rated replacement, you’re ready to complete the repair by swapping in the new fuse. Follow these careful steps:
1. Unplug Microwave Again
Though you surely disconnected it already, double check that someone hasn’t accidentally plugged the unit back in. Reconfirm the power cord is pulled from the outlet.
2. Remove Old Fuse
Grip the blown fuse’s metal end caps firmly with insulated pliers and pull it straight outward to unclip it from the housing. For fuses lying loosely on board mounts, lift directly up instead.
3. Install New Fuse
Align your replacement fuse to fit into the clip or board housing gap left vacant after removing the faulty one. Push gently but firmly until it snaps securely into place, making flush contact at both ends.
4. Inspect Housing & Wiring
Before reconnecting power, carefully inspect wiring in the exposed panel area for damage. Look for cracked insulation, loose or burnt connections. Also, check components for signs of damage. These latent issues could have caused the initial fuse failure if present.
5. Replace Cover Panel
Screw the metal access cover you previously removed back into place over the fuse compartment. This protects inner circuits from contact and debris intrusion. Take care not to pinch any wires between panel edges as you reinstall screws.
6. Restore Power & Test
The moment of truth has arrived. Plug the microwave power cord back into the wall outlet and switch the unit on to verify proper operation. Listen and watch for the turntable and interior light to activate normally without issues.
Initially, the microwave may take a few seconds to display its clock again and respond to buttons after losing all power. As it reboots, things should come back on as expected. However, do NOT continue using the appliance if you notice any smoke, sparks or the fuse quickly blows again!
For continued safety after your fuse replacement, periodically check that microwave keys start and stop their cycle smoothly. Contact an authorized service company if problems persist.
Why Does a New Fuse Keep Blowing?
It can be endlessly frustrating if you insert a fresh fuse only to have it blow immediately or after using the microwave briefly. What gives?
When new fuses keep blowing, it almost always indicates an untreated fault elsewhere in the unit that places excess current demand on the replacement fuses, destroying them shortly after installation.
Here are the most common reasons the fuse may blow again after replacement:
- Another component, like the high voltage diode or capacitor, has failed. These parts exceeding normal current draw under fault and blow fuses.
- Damaged microwave generator system with shorted magnetron tube or transformer windings. This leakage also overloads the fuse.
- Intermittent short circuits due to malfunctioning door switches, bad contacts, or inner arcing between damaged wires/terminals shortening excessively when microwave runs heating cycles.
- Wrong fuse was installed that cannot handle appliance’s current load. Rare, but using an incorrect fuse type with lower amperage rating or slow blow feature instead of the fast-acting fuse required allows failure under normal operating loads.
When repeated fuse blowing happens despite installing new ones properly, the microwave requires service work to locate and replace the malfunctioning internal part responsible for excessive current demands that destroy replacement fuses.
Contact an experienced appliance repair company to troubleshoot and fix defects making fuses blow to get your microwave working safely again long-term.
When to Call a Professional
While handy homeowners may be comfortable replacing standard fuses that just occasionally blow, more complex microwave repair issues should be handled by qualified technicians.
Seeking professional assistance is recommended in situations like:
- You cannot safely access the fuse area without partially dismantling the unit
- The same new fuse blows immediately more than once
- There are signs of damaged wires, components or scorch marks
- The appliance makes abnormal noises, sparks or emits smoke
- Door alignment, switches or lock functionality are compromised
- Touchpad and controls are unresponsive after fuse replacement
- An error code appears when attempting to operate microwave after repair
Do not continue using any appliance exhibiting these common symptoms of larger electrical issues. Microwave repairs can quickly escalate in scope and danger. Let experienced service staff evaluate the situation to map needed fixes.
Many companies offer quick on-site visits with upfront estimates, which allow you to determine cost-effectiveness of repair vs replacement.
Conclusion
A blown fuse is one of the most fixable microwave issues, provided power is fully disconnected during installation of the new replacement fuse. This step-by-step guide equips you to locate your unit’s fuse, properly test and identify the right replacement, then conduct this basic repair to restore cooking functions.
However, remember that a repeatedly blowing fuse after changes indicates larger electrical faults are still present. Do not keep using a microwave that continues exhibiting problems. Seek assistance from appliance professionals whenever complications arise to ensure your repair work and unit usage stay safe.
Following cautious procedures and determining when to call a trained technician prevents putting yourself or loved ones at risk of harm. Learn to become comfortable with basic DIY electrical repairs using our visual guides, but recognize limitations too. Combining self-sufficiency and expert help at the right times makes household appliance repairs most effective.