Why will my garage door opener open the garage but not close it?

If your garage door opener opens garage but won't close it, the most common cause is safety sensor issue, as sensors are designed to prevent closing when obstruction is detected but do not prevent opening, making this classic sensor problem. Safety sensors are small boxes near bottom of door tracks, one sending infrared beam and one receiving, with LED lights indicating status. When sensors are misaligned, dirty, have loose wiring, or are blocked, receiving sensor LED blinks or goes off, and opener will open but refuse to close, often with opener light blinking 10 times to indicate sensor fault. To fix, clean sensor lenses with soft cloth to remove dirt, cobwebs, or debris, ensure sensors are aligned facing each other with no obstruction, and adjust by loosening wing nut and tilting until both LEDs are solid, not blinking, with sending sensor usually yellow and receiving green. Check wiring for loose connections at sensors and at opener unit, and ensure wires are not damaged by staples or rodents. Check for sunlight shining directly into sensor lens causing interference, and shade sensor if needed. Another cause is travel limits set incorrectly where close limit is too short. Try closing door by holding wall button down continuously, as holding overrides sensors temporarily and allows closing if sensors are issue, but fix sensors promptly for safety. If sensors are damaged, replacement sensors cost 20 to 50 dollars and can be installed DIY with same wiring.