Garage door opener hums but does not move the door; humming stops after a few seconds.

Safety first: Unplug the opener before inspecting the rail or trolley. Do not continue to run a humming motor; it can overheat and fail.

• Check door movement: Pull the emergency release and try to move the door by hand. If it is stuck, address track or spring issues before using the opener.
• Inspect trolley: Look along the Craftsman rail for a jammed trolley or broken stop bolt. Clear any obstructions and ensure the trolley moves freely when the opener is disconnected.
• Check chain/belt tension: If the chain or belt is extremely tight, loosen the tension nut slightly until there is a small amount of sag or deflection.
• Test capacitor: If the motor hums but will not start even with a free door and proper tension, the start capacitor may be weak or failed. Replace it with a Craftsman-compatible capacitor.
• Test operation: After corrections, reconnect power and run the opener. If humming persists, the motor itself may be failing and require replacement.