Diagnosis
That’s thermal expansion. The ceramic heating element and its metal housing expand at slightly different rates as they heat up, causing a series of clicks or pops. It’s very common with this type of heater and usually harmless.
How to Fix It
First, rule out anything loose. Unplug the heater, let it cool, and gently shake it. Listen for any parts rattling inside. If you hear something, you might need to open the case (remove the four bottom screws) and check that the ceramic element is securely mounted in its brackets and that all internal screws are tight. Usually, just tightening everything up will reduce the noise. If the noise is purely the expansion clicks, there’s no mechanical fix—it’s just how the materials behave.
If That Didn't Work
If the noise is more of a constant buzzing or crackling, not just initial clicks, you could have a small piece of debris (like a dust bunny or insect) inside the housing that’s touching the hot element. You’d need to open the case and use compressed air to carefully blow out the interior, especially around the ceramic block.
Heads Up
Never try to stop the noise by lubricating anything inside the heater. There should be no oil or grease near the heating elements or electrical components—it’s a fire hazard.