Microwave display shows E04 and the turntable does not rotate; sometimes a grinding noise is heard from the bottom.

Safety first: Unplug the microwave before inspecting the turntable mechanism.

• Check for mechanical obstruction: Remove the glass tray and roller ring. Clean any spilled food or debris from the cavity floor. Inspect the roller ring for cracks or flat spots and replace if damaged.
• Inspect the coupler: The plastic coupler that fits over the turntable motor shaft can crack or strip. Remove it and check for damage. Replace if worn or broken.
• Test the turntable motor: Access the underside of the microwave (often by removing the bottom cover). Disconnect the turntable motor and test its resistance with a multimeter. An open circuit or very high resistance indicates a failed motor.
• Replace motor if needed: Install a Telefunken-compatible turntable motor with the same voltage and shaft type. Refit the coupler, roller ring, and glass tray.
• Re-test: Plug in and run the microwave with a cup of water to confirm smooth rotation and that E04 no longer appears.