Top oven or auxiliary oven does not heat correctly, display shows F4 when that cavity is used.

Safety first: Isolate power and allow the cooker to cool.

• 1. Identify the affected cavity: Confirm that F4 appears only when the top/secondary oven is selected.
• 2. Locate the sensor: In the top oven, find the temperature probe at the rear or side. Remove its fixing screw(s) and gently pull the sensor into the cavity to access the connector.
• 3. Inspect and test: Check for damage to the sensor sheath and cable. With a multimeter, measure resistance at room temperature; compare with the main oven sensor if identical type. Open or very low resistance indicates failure.
• 4. Check harness routing: Ensure the cable is not touching grill elements or sharp metal edges. Re-route if necessary using existing clips.
• 5. Replace sensor: Fit a Rangemaster-compatible top oven sensor if readings are out of specification. Refit the sensor firmly to the cavity wall.
• 6. Control board check: If a new sensor does not clear F4, the fault may lie in the control board input for the secondary sensor.