Opener will not move the door; motor hums briefly then stops; diagnostic LED flashes four times repeatedly.

Safety first: Turn off power at the breaker and unplug the opener. Do not repeatedly cycle a stalled motor; it can overheat and cause damage.

Steps to diagnose motor overload:

• 1. Check door movement: Pull the emergency release cord to disconnect the door from the opener. Manually open and close the door. If it is heavy, jerky, or stuck, have the door hardware and springs serviced before working on the opener.
• 2. Inspect rail and trolley: With the door disconnected, slide the trolley along the rail by hand. It should move smoothly. Clean any hardened grease or debris from the rail and lightly lubricate with a silicone-based spray.
• 3. Examine carriage and stop bolts: Ensure the trolley is not jammed against the header stop bolt or opener head. Adjust the up/down limit stops if necessary to prevent over-travel.
• 4. Test motor without load: With the door still disconnected and power restored, activate the opener. If the motor still hums and stops, the start capacitor or motor itself may be failing.
• 5. Inspect start capacitor: Disconnect power again, remove the opener cover, and locate the cylindrical start capacitor mounted near the motor on many Stanley units. Look for bulging, leaking, or burnt odor. Replace with a Stanley-compatible capacitor of the same microfarad (µF) rating and voltage.
• 6. Call a technician if needed: If a new capacitor does not resolve the issue, the motor windings or control board may be defective and require professional replacement.