Hansa oven temperature knob turns but temperature does not change or is erratic on mechanical models.

Safety first: Disconnect power and ensure the oven is cool.

• Check knob and shaft: Remove the knob and verify that the thermostat shaft turns with it. Replace the knob if it is stripped.
• Inspect capillary: Follow the thin capillary tube from the thermostat into the oven cavity. If kinked, broken, or leaking fluid, the thermostat must be replaced.
• Test thermostat: Use a multimeter to check that the thermostat contacts open and close as the shaft is turned. Replace if faulty.

When to call a technician: Thermostat replacement can be complex and may require removing the oven; professional service is advisable if you are unsure.