What's happening
The door starts to close, then reverses and the opener light flashes. That's the safety sensors at the bottom of the rails refusing to agree the path is clear.
Five-minute fix
- Look at the two small boxes near the floor on each side of the door. Both have LEDs.
- One should be green (or yellow) solid — that's the sender.
- The other should be green solid — that's the receiver. If it's blinking or off, it can't "see" the sender.
- Wipe both lenses with a dry cloth. Check for spider webs, sawdust, or a leaf in the way.
- Gently bend the metal bracket so both lenses point straight at each other. The receiver LED should go solid.
Still won't close?
- Press and hold the wall button (most openers will override and force-close).
- Inspect the rollers and springs — broken spring? Stop. Call a pro. A broken garage door spring stores enough energy to kill.
Don't DIY
- Torsion or extension spring replacement
- Cables off the drum
- Door sagging or off-track