Kiln Troubleshooting Guide for Your Problems

Your kiln is the heart of your creative process, whether you're firing up glass pieces, ceramics, jewelry, or blades. But just like any hardworking tool, even the most reliable kiln can run into problems over time. Environmental conditions, normal wear, or simple setup issues can all play a part.

That’s why we put together this guide: to help you quickly identify what’s going on, walk you through practical checks, and get you back to creating with confidence. We’ll look at seven common issues and show you how to troubleshoot them step-by-step.

Here’s what we’ll cover:

• Kiln Power Issues

• Heating Problems

• Error Codes on Digital Controllers

• Thermocouple Readings

• Element Performance

• Cracked Firebrick

• Relay or Transformer Malfunctions

Let’s get started.

1. No Power

What You’ll Notice

You plug in your kiln, flip the switch… and nothing happens. No lights, no display, no sounds. If it’s unresponsive, you’re likely dealing with a power supply issue.

Start by checking the basics:

• Is the power cord fully plugged into a working outlet?

• Has the circuit breaker tripped?

• Can another appliance run from that same outlet?

• Location of the Kiln

If everything looks fine from the outside but your kiln still won’t turn on, the issue could be inside the unit, like a loose wire or a damaged power cord. And since kilns use high voltage, this is where we recommend calling in a professional to stay safe.

Quick Checks You Can Do

• Confirm the power cord is securely plugged in.

• Check your breaker box for any tripped breakers or blown fuses.
  Make sure the kiln’s power switch is flipped fully to the ON position.

• Try plugging in a different high-powered appliance (like a space heater) to see if the outlet itself is working.

Before you fire an electric kiln, ensuring the power source is stable and the connections are secure can help prevent unexpected shutdowns. If those steps don’t fix it, look over the cord. Frays, kinks, or any signs of melting are all red flags. A worn cord or a loose internal connection could be the culprit.

Common Causes

• Damaged cords or connectors: Fraying, breaks, or loose plugs can interrupt the power.

• Tripped circuit breaker: If your kiln draws more power than your circuit can handle, it’ll cut off automatically.
  Internal wiring issues: Over time, switches and wiring inside the kiln can fail due to heat or wear and tear.

How to Fix Power Problems

• Inspect the entire power cord and plug for any damage or loose connections.

• Reset any tripped breakers or replace blown fuses.

• If you’re comfortable doing so, check inside the kiln for loose wires or damaged terminals (but only if the kiln is unplugged and cool).

• Still nothing? Reach out to a qualified kiln technician. Working on high-voltage equipment without training can be dangerous.

Need a deeper dive? We’ve put together a full troubleshooting guide to help you walk through every detail safely and confidently:

[Link] Detailed troubleshooting guide for “No Power”

2. Heating Issues With the Kiln

What You’ll Notice

If your kiln is taking way longer than usual to heat up, or your finished pieces are coming out underfired in some spots and perfect in others, your heating system may need attention.

Here’s what might tip you off:

• Firing takes 25–50% longer than normal.

• One side of the kiln seems cooler than the other.

• The kiln won’t reach the programmed temperature.

• Some of your pieces are properly fired, while others aren’t.

Before you assume the kiln is the problem, double-check your firing schedule. Sometimes programming errors can produce similar results. But if everything’s set correctly and you’re still seeing uneven or sluggish heating, it’s time to dig in.

Quick Checks You Can Do

• Watch your heating elements during operation. They should glow evenly from end to end in a steady orange-red. If some parts are dim or completely dark, that element probably needs to be replaced.

• Look for gaps in the kiln’s door seals or vent plugs that aren’t sitting right. Even a 1/8-inch gap can throw off heat balance.

• Use a voltmeter to check the power supply. You’ll find the kiln’s voltage requirement on its label or in your manual. Most standard kilns run on 240 volts (±10V); smaller ones might use 120V. If your voltage is off, it can affect performance.

Common Causes

• Worn-out elements: Heating coils wear down over time, just like the burner on an electric stove. As they degrade, they take longer to heat up—or stop working altogether.

• Relay trouble: If the relay (the switch that tells the elements when to turn on) isn’t working correctly, your kiln can’t heat evenly.

• Power supply issues: Shared circuits or thin household wiring can starve your kiln of voltage. If your kiln is competing with a dryer or oven on the same line, that could be the culprit. Undersized wiring (like anything smaller than 10-gauge for 240V) also causes performance drops.

How to Fix Heating Problems

• Replace any elements that look discolored, warped, or have dead spots.

• Check your relays. If they’re not clicking on and off correctly during firing, they may need to be replaced.

• Make sure your kiln is on a dedicated circuit with the right wire gauge and amperage. You’ll find this info in your kiln manual.

Pro tip: Replacing elements and relays every 100–125 firings (or every 2–3 years) is a great way to stay ahead of problems, especially if you're firing at higher temps. It’s an investment, but it helps avoid ruined projects down the line.

Want a more detailed breakdown? Head over to our full guide on kiln heating issues:

[Link] In-depth guide on diagnosing heating issues

3. Error Codes

What You’ll Notice

Your kiln’s digital controller suddenly flashes an error code, or maybe the firing stops halfway through. These codes can look cryptic—something like “Err1” or “FAIL”—but they’re actually built-in signals that help you figure out what’s going wrong.

Other signs that your controller might be acting up:

• Unexpected shutdowns during firing

• The program skips steps or starts over

• The kiln doesn’t follow the schedule you entered

Even if everything looks fine physically, the issue may be behind the display. Think of your controller like a kiln’s brain—when it gets mixed signals, everything else can fall out of sync.

Quick Checks You Can Do

• Write down the exact error code you see, including any numbers or symbols. These codes are specific to your controller’s make and model, so the details really matter when troubleshooting.

• Try resetting the kiln. Unplug it for a minute or two, then plug it back in and restart the controller. This is basically the kiln version of “turning it off and on again”—and yes, it actually works for a lot of temporary glitches.

• Still getting that code? Check your kiln’s manual for an error code reference or reach out to the manufacturer’s tech support for guidance.

Common Causes

• Bad thermocouple readings: If your thermocouple is damaged or worn, the controller can get bad temperature data and throw an error.

• Voltage issues: Big spikes or drops in power, especially more than ±10% of your kiln’s voltage requirement, can trigger error codes to protect sensitive electronics.

• Controller hardware problems: Over time, the circuit board inside your controller can wear out, especially after repeated exposure to heat or power surges.

How to Fix Error Codes

• If the thermocouple is worn, corroded, or discolored, it’s time for a replacement. Accurate readings are essential for proper kiln performance.

• If your power supply tends to fluctuate, consider installing a voltage regulator. This keeps your controller from getting overloaded or starved of power.

• For software glitches, try a full factory reset (just follow your controller manual’s steps).
  

• If it’s a hardware issue, you might need to replace the controller or have its circuit board serviced. In either case, don’t guess—check your manual or give us a call. We’ll help you figure it out without the stress.

Want to see what your specific code means and how to fix it? Head over to our complete error code guide:

[Link] Comprehensive error code guide

4. Thermocouple Issues

What You’ll Notice

If your kiln’s temperature readings seem way off—or bounce around during firing—you’re probably dealing with a thermocouple issue. This little sensor reaches into the kiln chamber and tells the controller how hot things are getting. When it’s not working properly, it can throw everything out of whack.

Look for signs like:

• Temperature readings that are 25–50°F off from what they should be

• Fluctuating temps when the kiln should be holding steady

• Finished pieces that are overfired, underfired, or just inconsistent—even when you’ve programmed the same schedule as before

It’s frustrating when you do everything right but still get unpredictable results. That’s usually your kiln reacting to bad data from the thermocouple.

Quick Checks You Can Do

• Make sure the thermocouple is in the correct position. It should stick 1 to 1.5 inches into the chamber and remain mostly straight—no sharp bends.

• Check for any buildup, like glaze or kiln wash, on the tip. That can throw off temperature readings.

• Look at the wiring where the thermocouple connects to the controller. If you see corrosion (white or greenish powder), loose wires, or anything that looks off, that could be the issue.

Even a slightly loose or corroded connection can distort the temperature reading.

Common Causes

• Loose or oxidized connections: Over time, heat and moisture can break down the connection points, which interrupts the tiny electrical signal that sends temp data to the controller.
  

• Normal wear: Thermocouples naturally degrade after about 100–150 firings. This is called “drift,” and it just means the sensor slowly loses accuracy.

• Wrong type or settings: If your kiln controller is set for one thermocouple type (like Type K), but a different one is installed (like Type S or R), you’ll get wildly incorrect readings.

How to Fix Thermocouple Problems

• Tighten or clean any corroded connection points using fine sandpaper.

• If your thermocouple has reached the end of its lifespan or is physically damaged, replace it.

• Double-check your controller settings to make sure they match the type of thermocouple installed. (This info is usually in your kiln manual.)

As a rule of thumb, plan to test or replace your thermocouple every 75–100 firings to keep everything accurate. It’s one of the simplest ways to avoid costly misfires.

Want to go deeper? Our step-by-step guide walks you through everything you need to test thermocouples (and replace them). 

5. Element Issues

What You’ll Notice

If your kiln is suddenly taking 15–30% longer to fire, or some shelves are coming out perfect while others look underfired, your elements might be wearing out. Uneven heat distribution is one of the first signs that the heating coils need a little attention—or replacement.

Here are the key symptoms:

• Longer-than-usual firing cycles

• Cold spots or uneven heat zones inside the kiln

• Finished pieces show mixed results (some fully fired, others not)

• Parts of the heating elements don’t glow or glow dimly during operation

Element issues tend to creep up gradually, so it’s easy to overlook at first—until it starts affecting your work.

Quick Checks You Can Do

• Turn off and unplug your kiln, then take a look at each element. You're checking for:

• Visible gaps or breaks in the coils

• Thinner areas (especially if a section looks 30% skinnier than the rest)

• Coils that have popped out of their grooves or mounting pins
  
  

• Use a multimeter to test each element’s electrical resistance (measured in ohms). If the reading is significantly off from the manufacturer’s spec—by more than 10%—that element likely needs replacing.

We’ve got a guide that walks you through resistance testing step-by-step, even if it’s your first time using a multimeter.

Common Causes

• Normal wear and tear: Every time your kiln heats up and cools down, the elements slowly oxidize and crystallize. This causes them to get brittle and lose efficiency over time.

• High firing temperatures: Firing to Cone 9 or 10 regularly shortens element life more quickly than staying in the Cone 04–06 range.

• Electrical issues: Loose connections, corroded terminals, or voltage drops can limit how much power reaches the elements, causing uneven heating and accelerating wear.

How to Fix Element Problems

• Replace any elements with visual damage or resistance readings outside the recommended range.

• When installing new elements, clean all terminals and use anti-oxidation compound to keep the connections stable. Tighten everything to the manufacturer’s torque specs—usually 20–30 inch-pounds.

• Stay ahead of problems by tracking your firing history and planning replacements around 80–120 firings for high-fire use, or 120–150 for low/mid-range work.

Pro tip: Scheduling element replacements before a big project or busy season helps avoid mid-firing failures that can waste your time and materials.

Need help testing or changing your elements? Check out our complete guide:

[Link] Element testing and replacement instructions

6. Brick Cracking

What You’ll Notice

You open your kiln and spot cracks in the firebrick lining. Some are tiny hairlines, while others might look deeper or even run across multiple bricks. Not all cracks are cause for concern, but some can affect performance if left unchecked.

Here’s what to look for:

• Hairline cracks (under 1/16 inch wide): usually cosmetic

• Deep or wide cracks (over 1/8 inch), especially ones that cross multiple bricks

• Chipping, erosion, or missing brick pieces

• Areas that look like they’re crumbling or getting powdery, especially on the floor

If cracks are starting to grow or heat seems to be escaping faster, it’s time to take action.

Quick Checks You Can Do

• Let the kiln cool completely, then carefully inspect all interior surfaces.

• Pay extra attention to the floor—this area takes the most stress from loading and unloading.

• Document any cracks wider than 1/16 inch or areas where the brick is breaking down by more than 1/4 inch.

• Check for patterns: if cracks form a network or affect more than 10% of the interior, that’s a structural issue, not just cosmetic.

Common Causes

• Thermal shock: Rapid temperature changes (especially faster than 270°F per hour) can cause the brick to crack, just like glass would if exposed to a sudden shift.

• Mechanical damage: Loading shelves too forcefully, dropping tools, or scraping the walls with kiln furniture can chip and weaken the bricks.

• Firing fatigue: After many high-temp firings (especially Cone 6 and up), firebrick starts to break down at the microscopic level. It becomes more brittle and prone to damage.

How to Fix Brick Cracks

• For moderate damage, use high-temp kiln cement designed specifically for firebrick. It should match or exceed your kiln’s maximum firing temperature.

• If more than 15% of your interior brick is damaged, or the cracks are causing heat loss, consider scheduling a full brick replacement with a professional.

Preventing future cracks:

• Use a slow ramp rate (150–200°F / 65–93°C per hour) during key transitions like quartz inversion (around 1060°F / 571°C).

• Avoid opening the kiln too early during the cooldown.

• Be mindful while loading. Always leave at least 1 inch (2.5 cm) of clearance between your pieces and the elements or walls.

Want to learn how to patch cracks or spot when it’s time for professional repair? Visit our maintenance guide:

[Link] Brick repair and maintenance guide

7. Kiln Relay Issues

What You’ll Notice

If your kiln struggles to stay at the right temperature—or one section of the chamber feels much cooler than the rest—it might be a relay issue. Relays are the components that turn your heating elements on and off during firing. When they start to fail, your kiln can’t regulate heat properly.

Here are a few telltale signs:

• The kiln can’t hold a steady temperature (drifting ±15°F / ±8°C or more)

• Temperature spikes or dips—more than 20°F / 11°C swings—during a hold

• A whole section of elements isn’t working at all

• You no longer hear the usual clicking sounds from the control box

These issues often come on slowly, but once a relay goes, it can affect everything from firing consistency to overall kiln safety.

Quick Checks You Can Do

• Listen to your kiln during firing. Relays make a gentle, rhythmic clicking sound as they switch on and off—typically every 5 to 15 seconds.

• If a relay starts buzzing, clicking erratically or goes silent entirely, that’s a sign it’s sticking or failing.

• With the kiln unplugged and safely cooled, inspect the relays in the control box. Look for:
  
  

• Melted plastic or discoloration (especially black or blue marks)

• Burned or corroded terminals

• Misshaped or warped components

Common Causes

• Worn contact points: Relays wear out over time—kind of like a light switch that’s flipped thousands of times. Corrosion, pitting, or sticking can prevent proper power delivery to the elements.

• Overheating: If the relay compartment isn’t well-ventilated, or the relays are handling more current than they’re rated for, they may overheat and fail sooner.

• Power supply issues: Voltage spikes or brownouts stress relay components and shorten their lifespan.

How to Fix Relay Problems

• Replace any relay that shows signs of damage or irregular behavior—these parts aren’t meant to be repaired, just swapped out.

• While you’re in there, clean the terminals with an electronic contact cleaner, or use a wire brush to clean the contacts thoroughly. Thentighten everything to spec (usually about 20 inch-pounds).

• For added protection, consider installing a surge protector or voltage stabilizer to help prevent future damage from power fluctuations.

If relay problems keep coming back, have a technician check whether the installed relays are properly matched to your kiln’s power requirements. Sometimes, an undersized relay or poor electrical setup can cause premature failure, even if the replacement part is brand new.

Need a walkthrough on relay testing and replacement? We’ve got you covered:

Related: Kilns vs. Ovens vs. Furnaces | What's the Difference

A Little Maintenance Goes a Long Way

Staying on top of your kiln’s maintenance doesn’t have to be complicated—or stressful. A few simple checks, some routine care, and knowing what to look for can prevent the most common issues before they disrupt your creative flow.

And when something feels off? Don’t guess. Reach out, dig into our guides, or let a professional take a look. We’re here to help you keep creating confidently, with tools you can count on.