Garage door will not close from wall button or remote; opener lights flash once and the door reverses to open position.

Safety first: Disconnect power to the Craftsman opener at the outlet before touching wiring. Do not bypass safety sensors for regular use; they prevent injury and property damage.

• Check for obstructions: Inspect the area between the two safety sensors (mounted near the bottom of the tracks). Remove any boxes, tools, leaves, or cobwebs blocking the beam.
• Clean the lenses: With power off, gently wipe each sensor lens with a soft, dry cloth. Avoid solvents that can scratch plastic.
• Verify alignment: Turn power back on. The sending sensor LED should be solid; the receiving sensor LED should also be solid when aligned. Loosen the wing nut on each bracket and rotate the sensor until both LEDs stay solid when the door is moving.
• Inspect wiring: Follow the low-voltage wires from each sensor back to the opener head. Look for staples driven through the wire, cuts, or corrosion at the terminal screws. Repair damaged sections with low-voltage garage door wire and wire nuts, then tighten terminal screws firmly.
• Test operation: Press the wall button. If the door now closes normally and the lights no longer flash once, the issue is resolved. If the receiving sensor LED will not stay lit even when aligned and wiring is good, replace the faulty sensor pair.