LiftMaster · Garage Door Opener Moderate

1-4 — Safety sensors misaligned

Both sensors have power but the invisible beam is blocked or the sensors are not pointed at each other. The receiving (green) LED is off or flickering.

Keep using it?
Yes, with caution
DIY difficulty
Easy
Typical cost
$25-40
Verified against
liftmaster.com ↗

The fix

LiftMaster Safety Sensor Kit (041-0136, replaces 41A5034)

Safety sensor beam blocked or sensors not aligned

$25-40 easy difficulty 30 min Tools: screwdriver

Diagnose first: Loosen the wingnuts and re-aim both sensor eyes toward each other until the receiver LED goes solid before spending money on a new kit.

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How to fix it

  1. Clear any visible obstructions in the beam path.
  2. Wipe both sensor lenses with a soft, dry cloth.
  3. Loosen the sensor bracket wing nut and rotate the sensor until the green LED is steady-on.
  4. Tighten the wing nut without bumping the sensor.
  5. If direct sun is the cause, install a sun shield or relocate the sensor to the opposite jamb.
  6. Make sure both sensors are mounted no more than 6 inches above the floor.
  7. Verify with a test close cycle from the wall button.

Why it happens

Typical signs: Door reverses while closing or will not close · Up arrow blinks 1, down arrow blinks 4 · Green sensor LED off, dim, or flickering · Amber sender LED is on solid · Wall console shows Sensor or beam blocked message

  • Sensor bracket bumped or sagging Sensors knocked out of alignment by hitting them with a tool, ladder, or trash can.
  • Obstruction in beam path Cobweb, leaf, snow, sports gear, or stored item blocking the beam.
  • Direct sunlight on receiver Low morning or evening sun blinding the green eye.
  • Dirty sensor lens Dust, pollen, or grime on either lens.
  • Loose wing-nut bracket Bracket can rotate and lose aim over time.

More LiftMaster garage door opener codes

1-1 1-1 — Safety Sensor Obstructed, Misaligned, or Disconnected 1-2 1-2 — Safety sensor wire shorted or reversed 1-3 1-3 — Door control or wire issue 1-5 1-5 — No RPM Detected at Start of Movement 1-6 1-6 — Unexpected RPM After Stop at Open 2-1 2-1 — Logic Board Component Failure

All LiftMaster codes → All garage door opener codes →

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: liftmaster.com.