DIAGNOSIS This is the internal thermostat cycling on and off to maintain the set temperature. A soft click every few minutes is normal. A loud, rapid, or constant clicking is not.
FIX Confirm the noise is the standard thermostat click. It should be a single, muted *click* when heating engages and another when it disengages. This correlates with the heating light turning on and off.
IF THAT DIDN'T WORK A loud, repetitive ticking may be a loose component vibrating from the fan. Unplug, cool, and check that the rear fan cover is securely fastened and that no utensil or foil is contacting the fan.
HEADS UP If the clicking is accompanied by sparking, a burning smell, or the unit turning off, unplug immediately. This indicates an electrical fault.