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Why won't my garage door close, and how do I fix the sensors?

Updated August 2026

15–20 minutes · Easy DIY

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A door that starts down, stops, and rolls back up while the opener light blinks is almost always reporting a broken photo-eye beam, and clearing it takes 15–20 minutes with a rag and a screwdriver. The two sensors sit about 6 inches off the floor on each vertical track. Wipe both lenses, pull whatever is in the beam path out of the way, then loosen one bracket and nudge the sensor until both LEDs burn steady instead of flickering. Federal safety rules have required this reversing system on residential openers since 1993, so any opener from the last three decades has a pair.

What you need

Before you start: The photo eyes are the last thing standing between a child or a pet and a door slab that weighs 150–400 pounds, so never tape the sensors face to face or hold the wall button to force the door down as a workaround. Keep your hands off the torsion spring above the opening and off the bottom-bracket bolts at each corner; both hold hundreds of pounds of stored energy and are technician-only. If the door closes but does not reverse when it meets an obstruction, the force setting is wrong and that is a service call, not a sensor problem.

Steps

  1. Read the opener before you touch anything. Most brands flash a fault code on the motor unit light or the wall control, and the legend printed inside the housing tells you whether it is reporting the safety eyes or the logic board.
  2. Clear the beam path and sweep the cobwebs off both brackets. One web strung across a lens scatters enough light to trip the sensor.
  3. Wipe both lenses with the dry cloth. Skip solvents and glass cleaner, which haze the plastic permanently.
  4. Read the LEDs. The sending eye shows a steady light whenever it has power; the receiving eye is steady only while it sees the beam. A dark, dim, or flickering receiver is your target.
  5. Loosen the wing nut on the receiver bracket, hold the sensor, and sweep it slowly left, right, up, and down until the LED locks solid. Tighten the fastener without letting the sensor drift.
  6. Confirm both eyes sit within a quarter inch of the same height and no more than 6 inches off the floor. Stretch a string between the brackets if you cannot tell by eye.
  7. Trace both wires back to the motor unit. Look for a staple driven through the insulation, a wire pinched behind shelving, or rodent damage, and check that each conductor is clamped tight at the terminals.
  8. Test twice. Close the door with the wall button, then close it again and wave a broom handle through the beam. The door must stop and reverse. If it does not, stop using the opener and call a technician.

Or hire it out

A garage door technician charges $100–200 for a service call to realign sensors, and most of that is the trip fee. A replacement sensor pair is $30–60 in parts plus $75–150 in labor when a lens is cracked or a wire is chewed through. Alignment costs nothing but 20 minutes, so try it before you book anyone.

Done. Now the part everyone skips: doing it again on schedule. Log it in OnOtto and the next reminder for garage sensor fixes sets itself.

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Frequently asked questions

The door only refuses to close on sunny afternoons. Why?

Direct sun hitting the receiving eye washes out the beam it is looking for, so the opener reads it as blocked. It shows up in west-facing garages between roughly 4 and 7 p.m. and disappears at dusk. Shade the receiver with a short piece of PVC pipe slipped over it, a cardboard hood, or by swapping which side the sender and receiver live on so the receiver faces away from the low sun.

Both sensor lights are completely dark. What does that mean?

That is a power or wiring fault, not alignment. Check the breaker and any GFCI outlet feeding the opener, then look at the two low-voltage terminals on the motor unit and make sure the bare conductors are seated and not touching each other. A shorted or broken run is the usual culprit, and restringing 30 feet of two-conductor bell wire costs about $10. A full sensor pair is $30–60 if one is genuinely dead.

Can I bypass the sensors and just force the door down?

No. Openers built to the current safety standard will only close with constant pressure on the wall button, and defeating the eyes removes the feature that stops a closing door on contact. Use constant-pressure closing once to secure the garage if you must, then fix the beam the same week. Deferred garage door work has a way of compounding, as skipping garage door maintenance lays out.

The eyes are aligned and it still reverses partway down.

Then the door is meeting resistance rather than a broken beam. Pull the emergency release and lift the door by hand: it should glide and hold wherever you stop it. Binding at one point means a bent track, a flat-spotted roller, or a loose hinge. A door that slams down or feels like a barbell points at the springs, and garage door spring replacement is the page to read next.

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