05·RB-GAR
Runbook — Garage door won’t close
It goes down, stops, and comes back up. Nine times out of ten, two small plastic eyes near the floor are the whole story.
956 N Noble Loop · Showing Edition · Rev A · Aug 2026
Every garage door opener made since 1993 has a pair of safety sensors — photo eyes — mounted about six inches above the floor on each side of the opening. They shine an invisible beam across the doorway, and if anything interrupts it while the door is closing, the door reverses. That is not a fault; that is the feature working. Almost every "won’t close" call is a beam that is blocked, dirty, knocked out of alignment, or dazzled.
The one rule of garage doors
Never work on the springs or the cables. The torsion spring above the door stores enough energy to kill, and it does not care how careful you are. Broken spring, frayed cable, door hanging crooked, or a door that suddenly feels enormously heavy — hands off, call a garage-door technician. Everything else on this page is safe to try.
First, check — in this order
- Look at the two sensors near the floor. One at each side of the door opening, small plastic housings with a colored LED. Move whatever is in front of them — a trash can, a bike, a bag of compost, a coiled hose. This is the answer most of the time.
- Wipe the lenses. Garage dust, cobwebs, and road grime build up on both lenses and quietly reduce the beam until it fails intermittently. A dry cloth on both, thirty seconds.
- Check the LEDs. Both sensors should show a steady light. On most makes, one sensor’s light goes out or flickers when the pair is out of alignment. Gently rotate the misaligned one in its bracket until its light is steady again — they are usually held by a wing nut and adjust by hand.
- Check the sensor wires. Follow the thin wires from each sensor up to the opener. Look for a staple through the wire, a wire pulled loose from its terminal, or damage where the wall meets the floor. A loose sensor wire behaves exactly like a blocked beam.
- Consider the sun. Low direct sunlight shining straight into a sensor at certain times of day genuinely blinds it. If the door only misbehaves in the late afternoon, that is your cause — shade the sensor or reposition it slightly.
- Look along the tracks. A tool, a ladder foot, a stone, or a lump of ice in the door’s path will stop it. Check the floor line where the door lands, too.
- Watch what the door actually does. Does it reverse the moment it starts down (sensor), or does it touch the floor and then reverse (travel/force limits — a technician adjustment)? That distinction tells you which half of this page you are in.
- Try each control in turn. Wall button, remote, keypad, and the app. If the wall button works and the remote does not, it is a battery or a remote. If everything physical works and only the app fails, it is the Linear controller or the network — see below.
If you must close the door with a failed sensor
Most openers let you override the sensors by pressing and holding the wall button until the door is fully shut — the door closes only while you hold it, so you must be watching. Use this to secure the house at night, then fix the sensor properly. Never disable, bypass, or tape over the sensors as a permanent arrangement: they exist because children and pets used to be crushed by these doors.
Symptom → cause → fix
| Symptom | Likely cause | What to do |
|---|---|---|
| Starts down, immediately reverses, opener light flashes | Safety sensor beam broken, misaligned, dirty, or wired loose. The flashing light is the opener telling you so. | Steps 1–5 above. The flash count is a diagnostic code for most makes — note it before you call anyone. |
| Closes fully, then reopens | Down-travel or force limit set slightly wrong, or an obstruction at the floor line. | Clear the threshold. If it persists, the limits need adjusting — a technician job, or a documented adjustment on the opener depending on model. |
| Nothing happens from any control | No power to the opener. | Check the ceiling outlet the opener is plugged into and its breaker — see breaker trips. The garage circuit is often GFCI-protected, so look for a tripped GFCI outlet too. |
| Motor runs but the door does not move | The emergency release has been pulled — the red cord hanging from the trolley. | Re-engage it: with the door fully closed, pull the red cord toward the door (or per the label) and run the opener once; the trolley re-latches with a clunk. |
| Door is very heavy by hand, or there is a visible gap in the spring | Broken torsion spring. Often preceded by a bang like a gunshot. | Stop. Do not use the opener — it will burn out trying. Do not attempt to lift the door. Call a garage-door technician. |
| Door is crooked, a cable has come off the drum, or a roller is out of its track | Mechanical failure under tension. | Stop using it and call a technician. A door off its tracks can fall. |
| Remote or keypad stopped working, wall button fine | Battery, or the wall control’s lock/vacation mode is on. | Change the remote battery. Check the wall control for a lock button or padlock icon and switch it off. Then re-learn the remote if needed. |
| Loud grinding or screeching, door still works | Dry rollers, hinges, or bearings. | Not urgent. Lubricate the rollers, hinges, and springs with a garage-door lubricant — never grease the tracks themselves. |
| The app or voice control does not work; buttons all fine | The Linear controller or the house network — not the door. | Check the network first (internet down), then the Linear controller’s own status. The door itself is healthy. |
| The app shows the door open when it is closed (or vice versa) | The tilt/position sensor on the door panel has moved, lost its battery, or lost its link. | Check the small sensor mounted on the door itself. Replace its battery and confirm it is sitting flat against the panel. |
The Linear controller — what it is and is not
The smart-garage device in this house is a Linear controller mounted on the ceiling near the opener, on its own plug-in power supply, with a position sensor on the door. It does not replace the opener: it presses the button for you and reports whether the door is open or shut. That distinction matters when something goes wrong.
- If the wall button works, the door and the opener are fine — whatever is failing is the Linear controller, its link, or the network.
- If the wall button does not work, the Linear controller is irrelevant; fix the door first.
- The controller is powered from a nearby outlet, so a tripped garage GFCI takes out the smart control while leaving the opener itself working — a confusing but common combination.
Owner's edition
Full details in the owner's edition — serial numbers, configuration and identity details continue in the complete manual, handed to the buyer at closing.
Stop and call a pro when…
- Anything involves the springs or cables — a garage-door technician. Broken spring, frayed or slack cable, door off its track, door suddenly heavy. This is the one item in this whole manual where the correct DIY action is to walk away.
- The door closes on the floor and reverses, and adjusting nothing at the sensors helps — a garage-door technician to set the travel and force limits. Set wrongly, these defeat the door’s ability to detect a person underneath it.
- The opener makes grinding noises, or the gear feels stripped — a garage-door technician. Openers are repairable and it is usually a cheap gear kit.
- The opener outlet or its GFCI will not hold — a licensed electrician.
- Only the app is broken — that is not a garage-door problem. Work the internet runbook, then the vendor.
Twice a year, test the safety reverse: with the door open, lay a length of timber flat on the floor in the door’s path and close it. The door must touch the timber and reverse. If it does not, the opener needs adjusting before it is used again. This takes two minutes and is the only safety test in this manual that a family member’s life might depend on.
Related pages
- Smart-home account transfer — how to take over or reset the Linear controller, erase the previous owner’s remotes from the opener, and change the keypad code.
- Breaker trips — for the garage circuit and its GFCI.
- Internet down — when only the app is failing.
- Nice North America — Support Center
Linear is now part of Nice (formerly Nortek Security & Control); nortekcontrol.com now redirects here. Current official support home for legacy Linear garage products. - Nice / Linear — Garage door operators & accessories
Linear-branded garage product line and documentation. - Garage door opener manufacturer documentation
to add once the opener make and model are captured — including the flash-code table, the safety-reverse test, and the limit adjustment procedure for this specific unit.