How to Read Kiln Error Codes and Troubleshoot Problems | ProKilnSupply

How to Read Kiln Error Codes and Troubleshoot Common Problems

You've loaded your kiln, set your program, gone to bed, and woken up to find the firing stopped mid-cycle with an error code on the controller screen. It's a frustrating experience — but most kiln problems are diagnosable and fixable without an expensive service call. Here's a guide to the most common kiln issues and what to do about them.

E- or Err: Thermocouple Errors

The thermocouple is the temperature-sensing probe inside your kiln. It's one of the most common failure points because it lives in a very harsh environment — extreme temperatures, thermal cycling, and exposure to fumes.

Common thermocouple errors:

TC Fail or E-1/E-2: The controller is getting an open circuit reading from the thermocouple — meaning either the thermocouple wire has broken, a connection has come loose, or the thermocouple has failed entirely.

Reading too high or too low vs. witness cones: The thermocouple is reading inaccurately. This can happen as thermocouples age — they drift over time and need to be recalibrated or replaced.

Fix: Check the thermocouple connections first (power off the kiln, unplug it, and inspect the lead wires). If connections are secure and the problem persists, replace the thermocouple. They're inexpensive and a straightforward DIY replacement.

PF: Power Failure

PF means the kiln lost power mid-firing — either a power outage or a tripped breaker. The kiln has held its program in memory. Most digital controllers allow you to resume a firing after a PF error.

Check your breaker first. A kiln that trips the breaker regularly is either drawing more current than the circuit is rated for, or an element is failing and drawing uneven current. Have an electrician verify your circuit capacity.

FAIL or SLOW: Temperature Rise Failure

This error appears when the kiln fails to increase temperature at the rate the controller expects — most commonly because one or more elements has failed or is significantly degraded.

How to diagnose: With the kiln cold and unplugged, visually inspect all elements for breaks in the coil. A broken element will have a visible gap. You can also use a multimeter to test resistance across each element — a failed element will show open circuit (infinite resistance).

Fix: Replace the failed element. Running a kiln with a failed element puts extra strain on the remaining elements and will shorten their life.

STUC or Lid Open Errors

Some kilns have a lid switch that detects whether the lid is open. A STUC error can indicate the lid switch has failed or that the kiln lid isn't fully closed. Inspect the lid switch and its connection.

When to Call ProKilnSupply

If you've worked through the basics and are still getting errors, call or text us at (801) 839-5882. We can help you interpret specific error codes for the brands we carry — Olympic, Evenheat, Jen-Ken, Cress, and others — and connect you with the right replacement parts or manufacturer support.