Garage door won't close? 7 causes and what to check

Before you start

Two safety rules. First, if the door is crooked, hanging, or there's a cable dangling, stop reading and don't touch it. That's an off-track door and it can fall. Second, never put your hands near the springs or the cables. Everything below is about the opener and the sensors, which are safe to look at.

It also helps to notice exactly what the door does. Does it not move at all? Start down and go straight back up? Make it most of the way and reverse at the bottom? Each of those points somewhere different, and the list below follows that order.

The 7 causes, in the order I check them

1. 1The safety sensors are out of lineLook at the two small boxes near the floor on each side of the door. Both should show a steady light. One blinking or dark means they can't see each other. Don't loosen or bend the brackets. Call me and I'll realign them. It's a quick job.
2. 2Something is in the beamA rake, a trash can, a spider web, a leaf. Low afternoon sun hitting a sensor straight on can do it too. Shade the sensor with a piece of cardboard and try again.
3. 3The wall button has lock mode onIf the remote won't work but the wall button will, someone pressed Lock. On most units you hold the Lock button for a few seconds to turn it off.
4. 4The travel limit driftedThe door goes almost all the way down and then reverses, because the opener thinks it hit the floor early. Limits are a setting on the opener, and setting them wrong can stop the door from reversing. Call me and I'll set them in a few minutes.
5. 5The force setting is too lowSame symptom as a travel limit, but the door reverses at a different spot each time. The door is binding somewhere and the opener gives up. That binding is usually rollers, track or balance.
6. 6The door is out of balanceIf the opener strains, the door comes down hard, or it rises unevenly, the springs may be off and the opener is being asked to do their job. Don't pull the release cord to test it yourself. Stop here and call, and I'll check the balance.
7. 7The spring is brokenA gap in the coil above the door, or one of two stretched springs along the tracks hanging loose. The door will feel very heavy. Don't try to close it with the opener. Call.

If the door is stuck open right now

If the sensors are the problem and you need the door down tonight, most openers will close the door if you press and hold the wall button until it reaches the floor. That bypasses the sensors, so watch the door the whole way and keep kids, pets and cars clear.

If the opener won't run at all, leave the door open and call me. Don't pull the release cord and try to lower it by hand. If a spring is weak or broken, the door can drop, and that's when people get hurt. In the meantime, lock the door between the garage and the house.

When to call

Two and three you can usually sort out without touching anything: move what's blocking the beam, or turn off lock mode at the wall button. The rest are mine. Sensor alignment, limits and force are quick fixes on a visit, and six and seven are spring problems. If it turns out to be the opener, my opener repair page covers what I fix and when a repair beats a replacement.

Sensor trouble is the most common of the lot, and I see it over and over in older Central San Diego garages where the brackets get kicked by bikes and bins. If yours keeps coming back, the guide to safety sensor problems goes deeper.

How to stop it happening again

Most of these causes come back because something keeps knocking the sensors or the door keeps drifting out of balance. A few habits help. Keep the floor near the sensors clear, and if they stick out where people walk, I can mount them on the wall side of the track. Test the auto-reverse once a month by laying a roll of paper towels in the doorway and closing the door: it should touch and go back up.

Once a year, have the balance checked, and look at the cables at the bottom corners for fraying, from a distance and without touching. A yearly garage door tune-up covers all of this, plus lube and a force-limit reset, and it's the easiest way I know to avoid a surprise.