Control knobs are very stiff or difficult to turn.

Safety first: Disconnect power before removing knobs or fascia.

Step-by-step checks:

• 1. Remove knobs: Pull the knobs straight off the shafts. Clean the knob bores and fascia with mild detergent.
• 2. Inspect shafts: Check for rust or melted plastic. Do not use excessive force to turn seized shafts.
• 3. Lubricate lightly: Apply a tiny amount of high-temperature-safe lubricant to the metal shaft (avoid getting any into electrical contacts).
• 4. Replace components: If shafts remain stiff, replace the affected thermostat or function selector switch and fit new control knobs if deformed.