A door that will not close is one of the most common calls we get, and it is also the one most likely to have a fix you can do yourself in five minutes. Work through these in order — they run from the most common and cheapest to the least common and most serious.
1. The photo-eye sensors
Since 1993, federal law has required every residential garage door opener to have photo-eye safety sensors mounted within six inches of the floor on both sides of the opening. One transmits an infrared beam, the other receives it. If the beam is broken, misaligned, dirty or unplugged, the opener refuses to close and reverses instead.
This is the cause the large majority of the time.
Look at the small LEDs on both sensors. What you want is two steady lights. What you usually find is one steady and one flickering, dim, or dark.
Check in this order:
- Something in the beam path. A bin, a bike wheel, a snow shovel, a bag of salt leaning against the wall. Move everything out of the opening and try again.
- Dirt on the lenses. Garage dust, cobwebs and road salt film build up over a winter. Wipe both lenses with a dry soft cloth. Not solvent, not glass cleaner sprayed directly.
- Alignment. The brackets bend easily — a knock from a car door or a snowblower is enough. Loosen the wing nut, move the sensor slowly until the LED goes steady, then retighten without shifting it. The two sensors need to be at the same height and pointed at each other.
- Sun glare. Late afternoon sun striking the receiver directly can swamp the beam. If the door only misbehaves at a particular time of day, this is why, and a small shade or a slight repositioning fixes it.
- The wiring. The low-voltage wire running along the wall gets nicked by tools, chewed by rodents, or pulled loose at the staple. Check the full run and the terminals at the motor head.
2. The down-limit setting
If the door goes all the way down, touches the floor, and then immediately reverses back up, the sensors are probably fine and the problem is the opener's down-limit — it believes it has hit an obstruction when it has actually just reached the floor.
Every opener has a limit adjustment, either as screws on the side of the motor head or as a programming sequence on newer units. The manual is specific to your model and it is worth finding.
3. The down-force setting
Related but distinct. The force setting tells the opener how much resistance to accept before assuming it has hit something. If it is set too sensitively, an ordinary bit of friction in the tracks reads as an obstruction.
A word of caution here: force settings exist for safety. Winding the force up until the door closes is exactly the wrong move — it defeats the mechanism that stops a door closing on a child or a pet. If the door needs more force than it used to, something has changed mechanically and the correct answer is to find out what.
4. Track obstruction and worn rollers
Look along both vertical tracks for a dent, a bent section, or a bolt that has worked loose and is protruding into the path. A roller with a broken bearing binds in the track, and the opener reads that resistance as an obstruction.
With the door closed and the opener disconnected, look at the rollers. Flat spots, chips, or a roller that wobbles in its stem all mean the same thing.
5. The door is out of balance
This one is not really a closing problem, but it presents as one. Pull the red release cord to disconnect the opener, then lift the door by hand to waist height and let go.
- Stays put — balance is fine, look elsewhere.
- Drops — the springs have lost tension.
- Rises — the springs are over-tensioned.
Either way, the opener is now fighting the door on every cycle, and it will express that as erratic behaviour before it eventually gives out. This one needs a technician; spring tension is not a homeowner adjustment.
6. The lock, the wall button, and the remote
Two mundane possibilities that catch people out.
The manual lock — the sliding bar that engages the track — may be partly thrown. Some doors have a vacation lock feature on the wall console that disables remotes entirely.
And the wall button held down: many openers will not close if the wall control is stuck or shorted, which can happen with a damaged low-voltage wire. If the remote works but the wall button does not, or the door only misbehaves when the button is nearby, that is the circuit to look at.
What the blinking lights mean
On LiftMaster and Chamberlain units, the light on the motor head blinks in patterns that are diagnostic codes. A steady flashing that will not stop very often means the safety sensors — again. The number of blinks maps to a specific fault in the manual, and reading it is normally the fastest route to the answer.
When to stop and call
Stop working through the list and call if:
- The door is crooked, hanging, or off its track. It is under load and unstable.
- There is a visible gap in the spring above the door.
- A cable is loose, frayed, or unwound from its drum.
- The motor runs but nothing moves — usually a stripped drive gear.
- The safety reversal test fails: with a solid object flat on the floor in the door's path, the door should reverse on contact, not push through.
That last one is the important one. If your door does not reverse when it meets an obstruction, stop using it until it is fixed. That mechanism is what stands between the door and whatever is underneath it.
Most of the calls we take for a door that will not close turn out to be a sensor alignment, and we would rather tell you that on the phone than charge you to come and wipe a lens. Describe what yours is doing and we will tell you straight whether it needs a visit.