How to Tell If a Ceramic Fuse Is Blown: Testing Methods

A ceramic fuse that looks perfectly intact can still be completely dead inside. The ceramic casing hides the internal wire, so the only way to know for certain is to test it with the right method.

What Is a Ceramic Fuse and Why Does It Fail?

A ceramic fuse is a cylindrical overcurrent protection device with a ceramic body encasing a thin metal wire or strip that melts when current exceeds a rated threshold. The ceramic material handles higher fault-current interruption capacity than glass fuses, which is why kilns, pottery wheels, and industrial studio equipment commonly use them.

The internal fuse element fails when current exceeds the fuse’s ampere rating, when a sustained overcurrent generates enough heat to melt the wire, or when a direct short circuit sends a surge through the circuit instantly. Ceramic fuses are rated in amperes (A) and voltage (V), both printed on the end caps.

Key Specifications for Ceramic Fuses in Studio Equipment:

• Common ratings: 1A, 2A, 5A, 10A, 15A, 20A
• Voltage ratings: 250V (standard) or 500V (high-voltage applications)
• Body diameter: 5mm x 20mm or 6.3mm x 32mm (most common in kiln controllers)
• Interruption capacity: up to 1,500A for ceramic vs 35A for standard glass fuses
• Cost range: $0.50 to $3.00 per fuse at electrical supply retailers

Ceramic fuses fail for four primary reasons: a genuine overload from drawing too much current, a short circuit in the connected equipment, age-related metal fatigue in the internal element, or voltage spikes from utility fluctuations. Identifying the cause before replacing the fuse prevents the replacement from blowing immediately.

How to Tell If a Ceramic Fuse Is Blown Without Any Tools

You can identify a blown ceramic fuse without a multimeter by using a visual inspection and a shake test, though these methods only catch obvious failures and miss partial breaks entirely. Start here before reaching for any testing equipment.

Visual Inspection of the End Caps

Remove the fuse from the holder with the power off and the equipment unplugged. Examine both metal end caps under a bright light or a focused LED inspection flashlight.

A blown fuse sometimes shows blackening, discoloration, or a burn mark on one or both caps. Severe short circuits often leave visible carbon deposits or a scorch mark on the ceramic body itself.

Discoloration is not always present. A fuse that failed from a slow overload rather than a hard short circuit may look completely clean on the outside while having a fully melted internal element.

The Shake Test for Ceramic Fuses

Hold the fuse close to your ear and shake it firmly. A rattling sound indicates the internal element has broken into separate pieces, which confirms a blown fuse.

No rattle does not mean the fuse is good. A melted element can fuse to the inside of the ceramic body, or it can vaporize entirely in a high-current fault, leaving nothing to rattle. Use the shake test as a quick confirmation, not a clearance test.

How to Test a Ceramic Fuse with a Multimeter

A digital multimeter is the most reliable and accurate way to test a ceramic fuse. Testing takes under 60 seconds and gives a definitive result regardless of what the fuse looks like externally.

Setting Up the Multimeter for Fuse Testing

Set the multimeter dial to the continuity setting, which is usually marked with a diode symbol or a sound wave icon. Most digital multimeters beep when continuity is present, making the test simple even in a noisy studio environment.

If your multimeter does not have a continuity setting, set it to resistance (ohms, marked with the omega symbol) on the lowest range, typically 200 ohms.

Step-by-Step Multimeter Test for a Ceramic Fuse

1. Power off and unplug the equipment completely. Never test a fuse while it is in a live circuit. Wait 30 seconds after unplugging capacitor-based equipment before handling internal components.
2. Remove the fuse from its holder. Use a fuse puller tool or needle-nose pliers wrapped with electrical tape to avoid damage to the ceramic body.
3. Touch the red probe to one end cap and the black probe to the other end cap. Apply firm contact to the metal, not the ceramic body.
4. Read the result. A good fuse reads 0 ohms to 2 ohms resistance and triggers the continuity beep. A blown fuse reads “OL” (overload), “1” (infinite resistance), or any value above 5 ohms, with no beep.
5. Confirm the result. Swap probe positions and test again. A single consistent reading confirms the result.

A reading of exactly 0.0 ohms with an immediate beep means the fuse element is intact and conducting. Any reading that climbs, fluctuates, or stays at infinite resistance means the fuse is blown and needs replacement.

What Resistance Values Mean in Fuse Testing

Use the table below to interpret your multimeter reading and determine whether the fuse needs replacement.

A fuse with any reading above 2 ohms should be replaced regardless of whether the continuity beep sounds. Elevated resistance in a fuse rated for 0 ohms means the element has degraded and will not provide reliable overcurrent protection.

The multimeter method gives you a definitive answer in under 60 seconds and costs nothing beyond the meter itself, making it the correct first test for any ceramic fuse in studio equipment.

How to Test a Ceramic Fuse with a Battery and Bulb Tester

A battery-and-bulb continuity tester works on the same principle as the multimeter continuity setting and costs less than $10. It uses a small battery, a low-voltage indicator bulb or LED, and two probe leads to complete a test circuit through the fuse.

You can also build a basic version using a 9-volt battery, a matching LED, and two alligator clip leads from any electronics supply retailer.

How to Use a Continuity Tester on a Ceramic Fuse

1. Confirm the tester works. Touch the two probes together. The bulb or LED should light immediately, confirming the tester’s own circuit is functional.
2. Touch one probe to each end cap of the removed fuse. Apply firm contact to the metal end caps only.
3. Read the result. Light on means the fuse is conducting and likely good. Light off means the fuse element is open and the fuse is blown.
4. Repeat with reversed probes. The result should be identical in both directions for a fuse.

A battery-powered continuity tester is a useful backup when a multimeter is not available, but it cannot measure resistance values. Use it for a pass/fail result only.

How to Test a Ceramic Fuse In-Circuit (Without Removing It)

In-circuit testing measures voltage across the fuse while the circuit is live, which identifies a blown fuse without removing it from the holder. This method requires the circuit to be energized and demands careful handling to avoid electrical contact with live conductors.

This approach is appropriate for experienced users testing equipment at the component level. If you are not comfortable working near live circuits, remove the fuse and test it out-of-circuit using the multimeter method above.

Voltage Drop Method for In-Circuit Fuse Testing

1. Set the multimeter to AC voltage (VAC) at a range higher than the circuit voltage. For a 120V circuit, use the 200V or 600V AC range.
2. Power on the equipment. The circuit must be live for this test.
3. Touch the probes to the metal end caps of the fuse while it is still in the holder. Keep probes on the metal caps only and avoid contact with any other components.
4. Read the voltage. A good fuse reads 0V across its terminals, because no voltage drop occurs across an intact conductor. A blown fuse reads the full supply voltage (120V or 240V), because the open element forces the full voltage differential across the break.

A reading of full supply voltage (120V on a 120V circuit) across a fuse in a live circuit is a definitive confirmation that the fuse is blown. A reading of 0V confirms the fuse is intact and conducting current.

In plain terms: a working fuse has no voltage difference across it because current flows straight through. A blown fuse blocks current completely, so the full circuit voltage appears across the open gap.

Ceramic Fuse vs Glass Fuse Testing: Key Differences

The testing methods for ceramic and glass fuses are identical in principle, but ceramic fuses require more reliance on electrical testing because the opaque ceramic body provides no visual information about the internal element. Glass fuses allow direct visual inspection of the fuse wire, which is not possible with ceramic types.

Use the table below to match the correct testing approach to your fuse type and available tools.

For ceramic fuses specifically, resistance measurement is the single most reliable out-of-circuit method because it catches partial element degradation that continuity tests and visual inspections miss entirely.

How to Safely Remove a Ceramic Fuse for Testing

Safe fuse removal requires the circuit to be fully de-energized before any contact with the fuse holder. This is not a step that can be skipped or shortened, even on low-voltage equipment.

Safe Removal Procedure Step by Step

1. Switch the equipment off using its main power switch.
2. Unplug the power cord from the wall outlet. For hardwired equipment, open the circuit breaker for that circuit and lock it out with a breaker lockout device.
3. Wait a minimum of 30 seconds for capacitors in motor-driven equipment such as pottery wheels and kiln controllers to discharge.
4. Use a plastic fuse puller or insulated needle-nose pliers to grip and extract the fuse from its holder. Do not use bare metal tools if any doubt exists about the circuit being fully de-energized.
5. Note the fuse rating printed on the end cap before testing. Write it down: ampere value, voltage value, and physical size. You need this to purchase an identical replacement.

Ceramic fuse holders in kiln controllers and pottery wheel foot pedals are typically panel-mount types accessed through a small access door or by removing a protective cover. Some holders are cap-and-spring designs that release with a quarter turn counterclockwise.

How to Read the Markings on a Ceramic Fuse

A ceramic fuse carries two mandatory ratings printed or stamped on its end caps: the current rating in amperes and the voltage rating. Replacing a fuse with a different rating is a safety hazard that can damage equipment or start a fire.

Decoding Ceramic Fuse Rating Codes

The current rating appears as a number followed by “A” (for example, 5A or 250mA for milliamp fuses). The voltage rating appears as a number followed by “V” (for example, 250V or 500V).

Some fuses also carry a speed rating: “F” means fast-blow (opens quickly on any overcurrent), “T” or “SB” means time-delay or slow-blow (tolerates brief inrush current before opening). Motor-driven studio equipment almost always uses time-delay fuses because motors draw high inrush current at startup.

Common ceramic fuse markings on studio equipment:

• F5A 250V: Fast-blow, 5 ampere, 250 volt (common in kiln controller logic boards)
• T10A 250V: Time-delay, 10 ampere, 250 volt (common in pottery wheel foot pedal assemblies)
• T15A 250V: Time-delay, 15 ampere, 250 volt (common in larger kiln controllers and element relay circuits)
• F2A 250V: Fast-blow, 2 ampere, 250 volt (common in signal and control circuits)
• T3.15A 250V: Time-delay, 3.15 ampere, 250 volt (IEC standard value, common in imported equipment)

Replacing a fast-blow fuse with a slow-blow fuse of the same ampere rating, or vice versa, changes the protection characteristics of the circuit and can allow overcurrent conditions to persist long enough to damage equipment. Always match the speed code as well as the current and voltage ratings.

What to Do After Confirming a Ceramic Fuse Is Blown

A blown fuse is a symptom, not the root problem. Replacing it without identifying the cause often results in the replacement fuse blowing immediately, or worse, allows a fault condition to continue damaging equipment.

Finding the Root Cause Before Replacing the Fuse

Inspect the equipment for visible signs of failure before installing a new fuse. Look for burnt components, melted insulation on wiring, a tripped motor thermal protector, or any component that appears damaged near the fuse holder.

For pottery wheels, a seized bearing or a locked rotor condition draws continuous high current until the fuse opens. For kiln controllers, a failed relay or a shorted element circuit can draw excessive current in the control board circuit.

If the equipment shows no visible damage, install an identical replacement fuse and power the equipment on immediately while observing the fuse holder. A fuse that blows again within seconds of startup indicates an active short circuit or a severely overloaded circuit that needs repair by a qualified electrician or equipment technician before the equipment is used again.

Choosing the Correct Replacement Ceramic Fuse

The replacement fuse must match the original in four specifications: current rating, voltage rating, physical size (5x20mm or 6.3x32mm), and speed rating (fast-blow or time-delay). Substituting a higher-ampere fuse to “solve” repeated blowing is a fire hazard and voids equipment warranties.

Purchase replacements from an electrical supply retailer or the equipment manufacturer’s authorized parts supplier. Ceramic fuse assortment kits covering common ratings from 1A to 20A at 250V are available for under $15 and keep the most common studio equipment sizes on hand.

Key Specifications When Buying Replacement Ceramic Fuses:

• Physical size: verify 5x20mm or 6.3x32mm before ordering
• Current rating: must match exactly (do not round up)
• Voltage rating: must equal or exceed circuit voltage
• Speed rating: must match original (F = fast, T = time-delay)
• Breaking capacity: IEC-rated ceramic fuses are marked with breaking capacity in amperes (1,500A minimum for studio equipment applications)

Ceramic Fuses in Specific Pottery Studio Equipment

Ceramic fuses appear in predictable locations across common studio equipment. Knowing where to find them saves time during troubleshooting and reduces equipment downtime during firing schedules.

Ceramic Fuses in Kiln Controllers

Digital kiln controllers such as the Skutt KilnMaster, L&L Easy-Fire, and Paragon Sentry use ceramic fuses in the control board circuit to protect the low-voltage logic components from power surges and relay failures. These fuses are typically rated between 1A and 5A at 250V and located on the controller’s printed circuit board or in an external fuse holder on the controller housing.

A kiln controller that displays nothing or fails to power on after a firing is frequently caused by a blown logic board fuse rather than a failed controller unit. Testing this fuse before ordering a replacement controller board can save $80 to $250 in unnecessary parts costs.

Key Specifications for Skutt KilnMaster Controller Fuse (current production models):

• Rating: 5A, 250V, fast-blow
• Size: 5mm x 20mm ceramic body
• Location: fuse holder on left side panel of controller housing
• Replacement cost: under $2.00 per fuse

Ceramic Fuses in Pottery Wheel Foot Pedals

Shimpo, Brent, and Skutt pottery wheels use ceramic fuses in their foot pedal assemblies or in the main power input circuit to protect the speed control board from motor overload conditions. These fuses are typically rated 10A to 15A at 250V, time-delay type, to accommodate the motor’s inrush current at startup.

A pottery wheel that powers on but produces no motor response, or that shuts off immediately when pressure is applied to the foot pedal, commonly has a blown fuse in the pedal or power input circuit rather than a failed speed control board.

Ceramic Fuses in Slab Roller and Extruder Motor Circuits

Motorized slab rollers and clay extruders use ceramic fuses rated to the motor’s full-load ampere rating, typically 5A to 20A at 250V, time-delay. These fuses protect the motor from sustained overload when clay is too stiff or when the equipment is operated beyond its rated capacity.

Check the equipment nameplate for the motor’s FLA (full-load ampere) rating when sourcing a replacement. The fuse rating should match or fall just above the FLA value listed on the nameplate.

Common Mistakes When Testing and Replacing Ceramic Fuses

Several recurring errors extend troubleshooting time, damage equipment, or create safety hazards. Knowing these mistakes before starting saves time and prevents compounding the original fault.

Testing a Fuse While Still Installed in a Live Circuit

Testing resistance or continuity on a fuse that is still installed in an energized circuit produces inaccurate readings because the parallel paths in the circuit influence the measurement. It also exposes the technician to electric shock risk from inadvertent contact with live conductors.

Always remove the fuse from its holder before testing with a multimeter on the resistance or continuity setting. The in-circuit voltage method described earlier is the only safe approach for testing without removal, and it requires the circuit to be live by design, with appropriate awareness of that risk.

Replacing a Fuse with a Higher Ampere Rating

Installing a 20A fuse in a circuit rated for a 10A fuse does not solve the problem. It removes the protection entirely, allowing fault currents up to 20A to flow through wiring and components rated for 10A maximum.

The result is overheated wiring, damaged circuit boards, melted insulation, and potential fire. The correct ampere rating is the only acceptable replacement, regardless of how many fuses of that rating have blown.

Ignoring the Speed Rating

Substituting a fast-blow fuse for a time-delay fuse in a motor circuit causes the fuse to open every time the motor starts, because motor startup inrush current is 5 to 8 times the running current for 50 to 300 milliseconds. A time-delay fuse tolerates this brief surge without opening.

A fast-blow fuse in a motor circuit is not providing protection against genuine faults. It is interrupting normal operation and masking the circuit’s actual protection status.

Assuming a Good Fuse Means the Equipment Is Fixed

A fuse reading 0 ohms on a multimeter means the fuse element is intact. It does not mean the equipment is functional or that no other fault exists. The fuse may be the only component that failed, or it may have blown because of a fault in a downstream component that remains present.

After confirming and replacing a blown fuse, test the equipment at low load before returning it to full operation. For kilns, run a test firing to a lower cone before a full production firing.

This section matters most for studio equipment used near ceramic materials, where kiln downtime during a firing cycle has direct consequences for work in progress. Identifying the correct replacement fuse the first time prevents repeat failures and avoids damage to bisqueware or glazed work mid-firing.

For studio safety practices with ceramic equipment, including what to check before and after a kiln firing, our guide to diagnosing and repairing common ceramic equipment damage covers inspection methods for kilns, wheels, and studio tools after electrical faults.

Tools You Need to Test Ceramic Fuses: A Complete List

The right tools make fuse testing a two-minute task rather than a guessing exercise. The minimum requirement is a multimeter and a fuse puller. Everything else speeds up the process or improves safety.

• Digital multimeter with auto-ranging: The primary testing tool. Select a model with a continuity beep function and a diode test mode. Budget models from Fluke, Klein Tools, or AstroAI in the $25 to $60 range are fully adequate for fuse testing.
• Plastic fuse puller: Removes ceramic fuses from spring-clip holders without damaging the ceramic body or bending end caps. Costs under $5 and prevents the most common fuse removal error.
• Insulated needle-nose pliers: For fuse holders where a puller does not fit. Ensure the insulation rating is at least 1,000V for any work near electrical panels.
• LED penlight or inspection flashlight: For visual inspection of end caps and fuse holder contacts in poorly lit equipment enclosures.
• Ceramic fuse assortment kit: Covering 1A, 2A, 3.15A, 5A, 10A, 15A, and 20A in both fast-blow and time-delay versions at 250V. Keep one kit in the studio near the kiln controller for immediate replacements during firing schedules.
• Lockout device for circuit breakers: Required for testing fuses in hardwired kiln or studio equipment where unplugging is not possible. OSHA 29 CFR 1910.147 requires lockout procedures for any work on electrical energy sources.

A complete fuse testing and replacement kit for a pottery studio costs between $30 and $70 and eliminates the most common cause of unplanned equipment downtime during production firing schedules.

If you work with lead-containing glazes on your fired ceramics and want to verify the safety of finished pieces in your studio, our guide on testing ceramic surfaces for lead content using home and lab methods covers both rapid test kits and laboratory analysis procedures.

How to Test a Ceramic Fuse: Quick Comparison of All Methods

Each testing method has a specific use case. The table below helps you choose the right approach based on the tools available and the situation.

Use the table below to select the fastest reliable method for your specific tools and safety situation.

For most studio pottery equipment, the out-of-circuit resistance test with a digital multimeter is the correct default method. It is safe, fast, and catches partial failures that the continuity-only method misses.

When your kiln or studio equipment is back in service, the next step is ensuring your glazed surfaces are safe for functional use. Our step-by-step guide on applying glaze to ceramic pots from bisqueware to finished surface covers application thickness, dipping consistency, and firing preparation for cone 6 and cone 10 results.

A dedicated digital fuse tester that shows both pass/fail and resistance is worth adding to a studio toolkit if you manage multiple kilns or troubleshoot equipment regularly. Units from Klein Tools and Fluke in the $20 to $40 range test all common fuse sizes with a single contact point on each end cap.

Frequently Asked Questions About Ceramic Fuse Testing

Can a ceramic fuse test good on a multimeter but still be faulty?

A ceramic fuse that reads 0 to 2 ohms on a multimeter is conducting correctly at the low current the meter applies, but a fuse with a partially degraded element may conduct at low test current while failing to carry rated load current. This is uncommon but possible in aged fuses with corroded end caps or mechanically stressed elements.

If a fuse tests good but the equipment still does not function, replace the fuse as a precaution and retest the equipment. A fuse that costs under $2.00 is not worth retaining when eliminating it removes all doubt.

What is the difference between a fast-blow and slow-blow ceramic fuse and can I swap them?

A fast-blow (F-rated) ceramic fuse opens within milliseconds of reaching its rated current. A slow-blow or time-delay (T-rated) ceramic fuse tolerates current surges up to 5 to 10 times its rated value for 50 to 300 milliseconds before opening. You cannot safely swap them in studio equipment.

Motor circuits in pottery wheels and slab rollers require time-delay fuses to handle startup inrush current without nuisance tripping. Substituting a fast-blow fuse blows on every startup. Substituting a slow-blow fuse in a circuit designed for fast-blow protection removes the speed of fault clearing that the circuit design requires.

Why does my replacement ceramic fuse blow immediately after installation?

A replacement fuse that blows within seconds of startup indicates an active fault in the circuit downstream of the fuse, not a fuse problem. The most common causes are a shorted element circuit in a kiln, a seized bearing in a pottery wheel motor, a failed relay contact welded in the closed position, or a shorted speed control board in foot pedal assemblies.

Do not install a third fuse until the downstream circuit has been inspected and the fault cleared. Continued fuse installation into an active short circuit is a fire and equipment damage risk.

Is there a difference between testing a 5A ceramic fuse and a 15A ceramic fuse with a multimeter?

The testing method and the result interpretation are identical for all ceramic fuse ampere ratings. A good 5A fuse and a good 15A fuse both read 0 to 2 ohms. A blown fuse of either rating reads infinite resistance. The ampere rating does not change the expected resistance of the internal element, as all fuse wire gauges are sized to read near 0 ohms at room temperature.

The only difference is the replacement specification. A 15A fuse must be replaced with a 15A fuse of the same speed rating and voltage. Never replace a 15A fuse with a higher rating to prevent repeated blowing.

Can I test a ceramic fuse without removing it from the holder if the power is off?

Testing a fuse in-circuit with the power off produces unreliable resistance readings because parallel circuit paths create alternative routes for the multimeter’s test current. The meter reads the combined impedance of the fuse and the parallel circuit, not the fuse alone.

A reading that appears to show continuity when testing an installed fuse in a powered-off circuit may be current flowing through a parallel path rather than through the fuse element. Remove the fuse from its holder before testing for accurate results.

How do I know if my multimeter is working correctly before testing a fuse?

Touch the two multimeter probes together with the meter set to continuity or resistance. A working meter reads 0.0 to 0.5 ohms and sounds its continuity beep immediately. Any reading above 1 ohm when the probes are shorted together indicates a low battery, a worn probe tip, or a defective meter.

Replace the battery and clean the probe tips with fine-grit sandpaper if the short-circuit reading is above 1 ohm. An inaccurate zero reading makes all subsequent fuse tests unreliable.

Are ceramic fuses in kilns a fire hazard if they fail in a specific way?

A ceramic fuse that fails in the open position (the normal failure mode) creates no fire hazard. The circuit is interrupted and the equipment stops operating. A fuse that fails in the short circuit or arc-over condition, which is rare but possible in high-fault-current events, can generate localized heat and carbon tracking inside the fuse holder.

After any hard short circuit in a kiln or controller, inspect the fuse holder contacts and the surrounding wiring for carbon tracking, melted insulation, or heat-deformed plastic before installing a replacement fuse. Replace the fuse holder if any of these signs are present.

Do ceramic fuses in kiln controllers need to be replaced on a regular maintenance schedule?

Ceramic fuses do not have a fixed service life under normal operating conditions and do not require scheduled replacement. A fuse in good condition in a correctly designed circuit can remain in service for many years without degradation.

Replace a fuse only when it tests outside the 0 to 2 ohm range, shows visible end cap discoloration, or has been exposed to a fault event such as a kiln relay failure or a short circuit. Keeping a spare assortment in the studio is practical preparedness, not a maintenance schedule.

Can I use a ceramic fuse in place of a glass fuse with the same rating?

A ceramic fuse and a glass fuse of identical current rating, voltage rating, speed rating, and physical dimensions (5x20mm or 6.3x32mm) are functionally interchangeable in most studio equipment applications. Ceramic fuses have a higher interruption capacity, which is a performance advantage, not a disadvantage.

Verify the physical size before substituting. A 5x20mm ceramic fuse does not fit a holder designed for a 6.3x32mm glass fuse. Forcing an incorrect size into a holder damages the contacts and creates unreliable electrical connection.

What does it mean if a ceramic fuse reads 0 ohms but the continuity beeper does not sound?

A multimeter showing 0.0 ohms without the continuity beep sounding typically indicates the continuity threshold on that meter is set above 0 ohms, usually above 10 to 30 ohms. Some meters activate the continuity beep only when resistance falls below their threshold, which varies by model.

A reading of 0.0 ohms on the resistance scale is a definitive pass result regardless of whether the beep sounds. Consult the meter’s user manual for its specific continuity threshold to understand when the beep activates on your model.

Is it safe to touch the ceramic body of a fuse to test it?

The ceramic body of a fuse carries no current and poses no electric shock hazard when the fuse is removed from its holder with the circuit de-energized. You can handle the ceramic body freely during out-of-circuit testing.

During in-circuit voltage testing with the equipment powered on, contact the metal end caps only with the multimeter probes and keep fingers away from the fuse holder area entirely. The end caps carry live voltage in an energized circuit.

If you have recently repaired ceramic studio equipment and need guidance on restoring damaged ceramic items, our guide covering repair methods for chipped and cracked ceramic items across different use cases covers adhesive selection, structural repair, and finish matching for both functional and decorative pieces.

Conclusion

A digital multimeter set to the resistance or continuity function is the only reliable way to confirm whether a ceramic fuse is blown, because the opaque ceramic body prevents any visual assessment of the internal element.

Remove the fuse from its holder with the circuit fully de-energized, contact both end caps with the probes, and confirm a reading of 0 to 2 ohms for a good fuse or infinite resistance for a blown one. Match the replacement to the original in current rating, voltage rating, physical size, and speed code before reinstalling, and inspect the downstream circuit for the fault that caused the original failure before returning the equipment to service.