Oven takes much longer than usual to preheat to the desired temperature

Safety first: Disconnect power before testing elements or wiring.

• Check which elements heat: During preheat, carefully feel (without touching directly) which areas of the oven get hot. If only one side or element heats, suspect a failed element.
• Test all elements: Measure resistance of the upper, lower, and circular elements individually. Replace any that are open or significantly out of spec.
• Inspect relays: On the control board, check for burnt or cracked relay solder joints. Resolder or replace the board if needed.
• Verify supply voltage: Have a qualified electrician check that the oven receives the correct mains voltage at the terminal block.