Safety sensors misaligned or momentarily obstructed

The 1 up-arrow, 4 down-arrow flash on a LiftMaster or Chamberlain opener is the most common code you'll hit: the sensors are wired correctly, but the beam between them broke or wavered. A bumped bracket, a dusty lens, low sun glaring straight into one eye at a certain hour, or something briefly crossing the opening all trip it. The tell is a door that starts down then reverses, often with one sensor LED flickering instead of glowing steady.

This is the friendliest code on the list to fix yourself and usually free. Wipe both lenses, clear the door path, and gently bend the brackets until both sensor LEDs are rock-steady — steady means aligned, flickering means the eye is just barely on target. If a specific time of day triggers it, shade the eye the sun hits. Only call a tech if the sensors keep dropping out after a clean alignment, which points to a failing sensor or wiring.

Meaning: The sensors are wired fine but the beam broke or wavered — misaligned brackets, a dirty lens, sun glare into one eye, or something briefly crossing the beam.
Likely fix: Wipe both lenses, clear the door opening, and bend/adjust the brackets until both sensor LEDs glow steady. If low sun hits a lens at the failing time of day, shade that eye.
DIY or pro: DIY-friendly — this is the most common code and usually a two-minute fix.

Both sensor LEDs steady = aligned. A flickering LED means the bracket is holding the eye just barely on target — bend it until the light locks solid.

Code tables vary by model year — confirm against your model's manual (model number is on the motor head, under the light lens). Unplug the opener before touching any wiring.

Frequently Asked Questions

Why does my garage door open but not close and flash?

That flash-and-reverse behavior is the safety-sensor system doing its job. The photo eyes near the floor either can't see each other (misalignment, a dirty lens, sun glare) or something is crossing the beam, so the opener refuses to close and flashes the 1-4 arrow code (or ten flashes of the main light on older units). Clear the opening, wipe both lenses, and align the brackets until both sensor LEDs glow steady, and it will close normally again.

How do I fix flashing sensor lights on a LiftMaster?

A flickering sensor LED means the eye is only barely catching its partner's beam. Loosen the bracket, aim the sensor directly at the opposite eye, and tighten it back down when the LED locks solid — no flicker. Wipe both lenses while you're there, since dust scatters the beam. If the light won't hold steady no matter how you aim it, check the wire run for staple damage; a persistently dark or flickering eye after alignment usually means a failed sensor.

Check another — Select your opener's flash pattern

Use the Garage Door Opener Blink Code Decoder to check any other option, or jump straight to one of these:

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