A door that will not close is almost always the opener refusing to send it down rather than the door failing mechanically. Watch what happens when you press the button, because the behavior sorts the fault into one of three groups before anyone picks up a tool.
Sort it by what the door does
Nothing moves and a light on the motor or wall console blinks: the opener is reporting a fault, normally in the safety circuit. Nothing moves and nothing blinks: look at power and at the lock button. The door starts down an inch and quits: physical resistance or a bad down limit. The door travels all the way down and rides back up: the opener believes it hit something at the floor.
The causes, most common first
- Photo eyes out of line or blocked. The two small lenses about six inches off the floor have to see each other. Knock one with a trash can and the beam breaks. Most brands show a steady LED when the pair is happy and a blinking or dead LED when it is not.
- Lock mode on the wall console. Many keypads have a lock or vacation button that kills remotes and blocks close commands. Holding it for a few seconds clears it. It gets pressed by accident more than anything else on this list.
- Something on the track. A bike pedal, a bag of potting soil, or a dried lump of mud on the track lip stops the door at the same height every attempt.
- Down limit stored past the floor. The opener keeps a floor position in memory. If it sits low, the door lands, motor load spikes, and the safety reverse fires.
- Cut sensor wire. The thin pair of conductors running along the wall gets nicked by a staple or a nail and shorts years later. Same symptom as a misaligned eye.
- Bent track or a flat roller. Genuine friction on the way down reads as an obstruction to the motor.
Safe to check, and what is not
Wiping the lenses with a dry cloth, sweeping the track, clearing the lock button and following the sensor wire with a flashlight are all reasonable. So is counting the blink pattern on the motor light.
Leave the counterbalance alone. The torsion spring above the opening, extension springs along the tracks, both lift cables, the drums at each end of the shaft and the bottom brackets are loaded whenever the door is down. Take a bolt out of a bottom bracket and that load releases through the cable fast enough to break a hand. None of it is a job for household tools.
What the repair tends to cost
Sensor alignment or a replacement eye pair runs an estimated $95 to $185. A diagnostic with a small adjustment sits at an estimated $89 to $175. If a worn roller set is the drag, most homeowners pay an estimated $125 to $225. Guide figures, not quotes.
Work through the LED, the lock button and the track first. If the door still refuses to go down, note the blink pattern and how far it travels before quitting, then have the limits and force set properly against a balanced door.