Opener hums but the door does not move; after a few seconds the motor stops.

Safety first: Unplug the opener before removing covers. Capacitors can hold charge; discharge safely if replacing.

• Check door movement: Ensure the door moves freely by hand with the opener disengaged.
• Inspect capacitor: Locate the motor capacitor in the Merlin opener. Look for bulging, leaking, or cracked casing. Replace with the exact µF and voltage rating specified.
• Spin test: With power disconnected and belt/chain removed (if possible), try turning the motor shaft by hand. If it is stiff or seized, the motor must be replaced.
• Test after replacement: Reassemble, restore power, and run a test cycle. If the motor still only hums, further diagnosis of the motor and board is required.