Why is my Kiln or Oven Not Heating Properly?
We all love our kilns and heat treat ovens. I'm even thinking about creating a big sign for Gail's studio that says "Have you hugged your kiln today?"💖 But, let's be honest... using a kiln comes with its share of emotional ups and downs. Knowing how to be a good troubleshooter can help at the time when you are starting to feel the most frustrated.
The good news? Most kiln/oven heating problems demonstrate clear warning signs: inconsistent temperatures, slow preheat times, or a complete failure to heat. So, let's look at some kiln troubleshooting tips from our friends @ Evenheat!
In this guide, we'll walk you through the most common culprits, how to spot them, and what you can do to get things working again.
Common Reasons Your Kiln/Oven Isn't Heating Properly
Power Supply Problems
Start with the basics: Is your kiln or oven receiving the power it needs? It sounds obvious, but even the most seasoned artists and makers get tripped up by a loose plug or tripped breaker. Check that the unit is securely plugged in and that the circuit breaker hasn’t tripped
Take a quick look at the unit's fuse, also. If it’s blown, your unit will stay cold no matter what else you do.
If everything looks good on the surface but your kiln or oven still won’t heat, inspect the outlet. Outlets can degrade over time and might not deliver the proper voltage. Most home ovens run on 240 volts. Kilns usually need between 208 and 240 volts, depending on the model. Testing the outlet can tell you if the issue is electrical.
Worn-Out Heating Elements or Igniters
In electric ovens, the heating elements are those glowing orange coils. If they don’t glow or have visible damage (blisters, cracks, or burn marks), it’s time for replacement. Kilns use heating elements made from high-resistance wire coiled along the walls. These wear out over time due to the extreme temperatures they endure. If sections of the wire look thin, worn down, or broken, they’re not doing their job.
A good rule of thumb: if the wire has lost about 25% of its original diameter in places, it’s time to swap it out. When considering how to fire an electric kiln, it's essential to ensure that all components, especially the heating elements, are in good condition to achieve consistent and safe firing results.
Gas ovens rely on igniters, which should emit a strong glow to ignite the flame. A dim or inactive igniter means the system won’t heat correctly.
Temperature Sensors or Thermocouples Gone Bad
Kilns use temperature sensors to manage internal heat. Kilns for Glass Fusing, Ovens for Heat Treating, and Pottery kilns all rely on thermocouples—sensors made from two dissimilar metals joined at one end—to send temperature data to the controller. These workhorses measure everything from warm glass-fusing ranges (1100–1700°F / 593–927°C) to high-fire ceramics and metal processing (up to 2400°F / 1316°C). Over time, thermocouples degrade, leading to inaccurate readings. If your kiln seems to fire too hot or not hot enough, and the readings are off by 50–100°F (10–38°C) or more, replacing the thermocouple is likely your fix.
A good rule of thumb is to change the thermocouple every five years, no matter what. After five years, the lifespan of the part is considered unreliable.
Relay or Control Panel Failures
Think of the control panel as the brain of your kiln or oven. It tells your unit when to heat up and when to cool down. Inside that panel are relays—small electrical switches that turn your heating elements on and off.
When relays fail, your kiln might not heat at all, or it might get stuck in the "on" position. That can cause serious overheating, which is not only a fire risk but can also ruin your work. If your kiln continues heating beyond its set point or behaves erratically, you’re likely dealing with a stuck or failed/failing relay. You can change these out yourself if necessary, as it’s a swap-out, then swap-in situation.
Door or Lid Switch Issues
Heat doesn’t stand a chance if it’s escaping from a faulty seal. For ovens, make sure the door closes tightly and that the rubber gasket is intact. If the gasket is cracked or loose, heat will leak out and force the unit to overwork.
Many kilns come with a door or lid safety switch that must be fully engaged for the heating cycle to start. If debris (like clay dust or glass frit) interferes with this connection, your kiln might act like the lid/door is still open and refuse to heat. Check around the perimeter of the door or lid for blockages, check your hinges for tightness, and your latch for proper closure, and make sure the switch clicks securely into place.
And speaking of lids? Knowing when it’s safe to lift the lid is just as important. Opening too early can cause thermal shock, especially with delicate glass or ceramics.It can ruin even the best metal processing as well. Always wait until the kiln has cooled to a safe temperature—typically below 200°F (93°C)—unless your specific process calls for a controlled venting/air quenching step.
Related: Kiln Troubleshooting Guide for Your Problems
When to Call in a Professional
Some issues are DIY-friendly, but others require professional eyes. If you've walked through all the basic checks—power, elements, sensors, and door seals—and your kiln or oven still isn't heating properly, it might be time to schedule a service.
This is especially important for anything involving gas lines or advanced electrical systems. Not only can those be dangerous, but you could also end up making the problem worse.
If your appliance makes strange noises, emits a burning smell, or repeatedly fails after your attempts to fix it, get help. Service fees typically range from $75–$250+ per hour, depending on your location and the type of technician needed. It's a worthwhile investment compared to replacing an entire unit.
A qualified tech can also catch subtle issues you might not notice, saving you time, money, and stress down the line.
Keep Your Kiln or Oven Running Smoothly
Heating issues can be intimidating, especially when you're in the middle of a project. But now that you know the most common causes, you can approach the problem with clarity and confidence.
Remember: start simple. Power supply, heating elements, thermocouples, relays, and switches are the usual suspects. Stay on top of regular maintenance like cleaning door seals, checking relays, and inspecting elements to keep everything running smoothly.
And when something feels outside your comfort zone? Trust your instincts and call in a pro. At Kiln Frog, we’re here to empower your creative journey with the tools and information you need—because we use this equipment too, and we know what it means when it doesn’t work right.
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