Oven heats but does not reach set temperature or takes excessively long to preheat.

Safety first: Turn off power before accessing internal components.

• Check door gasket: Inspect the oven door gasket for tears, gaps, or hardened sections. Replace if damaged to prevent heat loss.
• Visual element check: During a bake cycle, observe the bake element. It should glow evenly along its length. Dark spots or breaks indicate a failing element.
• Sensor test: Test the oven temperature sensor resistance at room temperature (~1080–1100 Ω). Replace if out of range.
• Calibrate (if available): Some Zline models allow temperature calibration in the settings menu. Use an oven thermometer to compare actual vs set temperature and adjust per the manual.

When to call a technician: If elements and sensor are good but temperature remains inaccurate, the control board may need replacement.