The photo eyes on either side of your garage door opening are the only thing stopping a 200-pound door from closing on a car, a bike, or a kid. When one of those little LEDs starts blinking, the opener has locked out the close cycle for a reason. The pattern tells you exactly what that reason is — if you know how to read it.
Most brands use a steady green light on the receiving eye and a steady amber, orange, or red light on the sending eye. Any blink, flicker, or colour change means the beam is interrupted, misaligned, or the circuitry has a fault. The chart below covers the residential openers we see on every truck in Metro Vancouver.
LiftMaster and Chamberlain (same parent company, same logic)
These two brands dominate the market. Their photo eyes have used the same diagnostic language for twenty years.
Sending eye (amber/orange/red)
- Steady on: Transmitter powered, sending beam.
- One blink per second: Wiring fault — usually a staple through the wire at the opener terminal or a nick in the insulation where it passes the hinge.
- Two blinks, pause, repeat: Shorted wires. The two low-voltage conductors are touching somewhere between the eye and the motor head.
- Four blinks, pause, repeat: The sending eye itself has failed. Rare, but it happens after a lightning strike or a power surge.
Receiving eye (green)
- Steady on: Beam received, path clear.
- One blink per second: Misalignment. The beam is not hitting the lens. Start here — it’s the cause 80 percent of the time.
- Two blinks, pause, repeat: Obstruction detected. Something is physically in the beam path — cobweb, leaf, stacked tote, or the door track itself if the bracket shifted.
- Four blinks, pause, repeat: Receiving eye failure. Internal circuit damage.
Both eyes blinking in unison Power cycle the opener. Pull the plug, wait ten seconds, plug it back. If the pattern returns, the logic board has a fault — not the eyes.
Genie (Intellicode / Safe-T-Beam)
Genie uses a single red LED on each eye. The colour never changes; only the blink cadence does.
- Steady red on both eyes: System happy.
- Sending eye blinking, receiving eye steady: Wire break or short on the sending side. Check the staples at the opener first.
- Receiving eye blinking, sending eye steady: Misalignment or dirty lens. Wipe both lenses with a dry microfibre cloth before you start twisting brackets.
- Both eyes blinking together: Power supply issue at the opener head. The 12 VDC feed to the photo-eye terminals has dropped out. Check the opener’s internal fuse or the wall-control wiring if the LEDs on the wall button are also dead.
Older Genie models (pre-2005) flash the wall-button LED instead of the eyes. Count the flashes: one flash is misalignment, two is a wire short, three is a faulty eye.
Craftsman
Craftsman openers built after 2005 are re-badged Chamberlain/LiftMaster units. The blink codes are identical to the LiftMaster chart above. Pre-2005 Craftsman units use a single green LED on the receiver only:
- Steady: Aligned.
- Slow blink (one per second): Misaligned.
- Fast blink (four per second): Wire short or receiver failure.
If you have a pre-2005 unit, the sending eye has no LED. You align by watching the receiver’s green light go steady.
Marantec
Marantec eyes have a single bi-colour LED on each unit: green for aligned, red for fault.
- Steady green both sides: Good.
- Steady red on one or both: Misalignment. Adjust until green returns.
- Red blinking once per second: Wiring fault — open or shorted circuit.
- Red blinking twice per second: Internal eye failure.
Marantec brackets are adjustable with a single thumb screw. Loosen, pivot until green locks on, tighten. Do not overtighten; the plastic housing cracks.
Linear (now Nortek / GoControl)
Linear eyes show a steady green receiver and steady amber sender when aligned.
- Amber sender blinking: Wire fault on sender side.
- Green receiver blinking: Misalignment or obstruction.
- Both blinking alternately: Communication error between eyes. Usually a crossed wire pair at the opener terminals — white/black swapped on one eye.
Stanley
Stanley hasn’t been made in years, but thousands are still on houses in Richmond and East Vancouver. Two LED styles exist.
Style A (two LEDs per eye, red + green)
- Green steady, red off: Normal.
- Red steady: Misalignment.
- Red blinking: Wire fault.
Style B (single LED per eye)
- Steady: Aligned.
- Blinking: Misalignment or wire fault — no further distinction. You troubleshoot by process of elimination: clean lenses, check alignment, then megger the wire if you have the tool.
Universal troubleshooting sequence (works on every brand)
1. Clean the lenses. Dust, spider silk, and pollen scatter the infrared beam. A dry microfibre cloth takes ten seconds. 2. Check the brackets. A bracket bent by a broom handle or a bike pedal moves the eye three degrees — enough to break the beam. Straighten by hand before you reach for a wrench. 3. Verify the wiring at the opener. The two low-voltage wires go to terminals usually labelled 1 and 2 or white and grey. No bare copper should touch the terminal next to it. No staple should pierce the jacket. 4. Test alignment in the shade. Bright sun hitting the receiver lens can wash out the IR beam. If the door closes at night but not at 2 p.m., shade the receiver with a piece of cardboard taped to the bracket. If that fixes it, replace the eyes with a newer model that has a sun shield. 5. Swap the eyes left to right. If the fault follows the eye, the eye is bad. If the fault stays on the same side, the wire or the opener terminal is the problem.
When to stop and call
- The opener clicks but the door doesn’t move — that’s not a sensor issue. Could be a broken spring, a stripped gear, or a locked trolley.
- You’ve cleaned, aligned, checked wires, and the blink code still says “eye failure.” The component is dead. We carry LiftMaster/Chamberlain, Genie, and Marantec replacement eyes on the truck.
- The logic board is throwing a code (both eyes blinking in unison on LiftMaster/Chamberlain, both blinking together on Genie). Board repairs are not DIY.
What we do on a sensor call
We verify the blink code, confirm the wiring with a multimeter, align with a laser pointer if the brackets are stubborn, and replace only the failed component. Flat-rate quote approved before we start. Two-year workmanship warranty on the repair.
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Call 778-873-7282 — Metro Vancouver.