Diagnose a Garage Door That Won't Close

Category: Mechanical · Difficulty: Beginner · Time: 1.1h · Estimated cost: $35

Tools needed

Check the safety sensors
Look for two small sensors mounted 6" off the floor on each side of the door track. Both should show a steady (usually green) LED. A blinking or off LED is your problem.
Duration: 5 min
Wipe the lenses
Wipe both photo-eye lenses with a microfiber cloth — spider webs and dust block the beam. Many 'broken' sensors are just dirty.
Duration: 5 min
Realign the eyes
Loosen each sensor's mounting bracket slightly. Aim them so they look directly at each other. Tighten when both LEDs go solid.
Duration: 15 min
Clear the track
Look at the floor along the door track — anything in the path (a leaf, a rock) will trigger the sensor and refuse to close.
Duration: 5 min
Inspect the rollers and springs
With the door OPEN and a ladder safely positioned, look at the rollers — they should be intact, not chipped. Look at the torsion spring above the door — if there's a visible gap (broken spring), STOP. Call a pro.
Duration: 10 min
Lubricate moving parts
Spray garage door lubricant on hinges, rollers (the bearings, not the wheels), and springs. Run the door up and down twice to spread.
Duration: 15 min
Test
Press the wall button. Door should close all the way and reverse if you wave a broom across the sensor beam.
Duration: 10 min

NEVER touch torsion springs — under enough tension to kill or maim. Broken spring = pro job, no exceptions.
Don't disconnect the opener arm with the door open — it will slam down. Lower it manually first.
Use silicone or lithium garage door lube only — WD-40 attracts dust and gums things up.

Broken springs, snapped cables, off-track door, or any opener motor noise/burning smell — call a garage door technician.