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The door opens fine, but pressing close makes it start down, stop, and travel back up — usually with the opener's light flashing. Or it won't close at all unless you hold the wall button down. Both symptoms point at the same place: the safety sensors. They're the most-blamed and least-understood part on a garage door, and most 'failed' sensors are dirty, nudged or sun-struck rather than broken. Work through this in order and there's a good chance the door is closing normally in five minutes.
How the sensors work
Look at the bottom of your door's tracks, about 10–15 cm off the floor: a small box on each side, facing each other. One projects an invisible infrared beam; the other receives it. While the beam arrives, the opener knows the doorway is clear and will drive the door closed. Break the beam — a child, a pet, a bike wheel — and a closing door stops and reverses. That's the safety system doing its job, mandated on modern openers for good reason. Holding the wall button down bypasses the sensors on most models, which is why that works when the remote doesn't — useful for diagnosis, not a way to live.
Fix 1: Clean the lenses
Perth's dust, spider webs, sprinkler over-spray and lawn clippings all end up on sensor lenses. Wipe both lenses with a soft dry cloth (a slightly damp one for grime, then dry). Check for webs behind and around the brackets too — a strand across a lens is enough. This alone resolves a remarkable share of sensor calls.
Fix 2: Check the indicator LEDs and realign
- Each sensor has a small LED. In a healthy pair, both are solidly lit (colours vary by brand — commonly one green, one amber/red).
- A dark or flickering receiver LED means the beam isn't landing. Sensors live at bumper-and-broom height, so brackets get knocked constantly.
- Loosen the wing nut or screw, aim the sensor squarely at its partner, and watch for the LED to go solid. Tighten gently — over-tightening twists the bracket off aim again.
- Confirm both LEDs solid, then test a normal close from the remote.
West-facing garage? Blame the sun
Low afternoon sun shining directly into a receiver lens can drown the infrared beam — the classic Perth pattern is a door that refuses to close on summer evenings but behaves by morning. A sun shield (or swapping which side the receiver sits) fixes it permanently.
Fix 3: Check the wiring
Sensor wires are thin low-voltage cable running from each sensor up to the motor — stapled along the wall and ceiling, exactly where brooms, rakes and stacked boxes catch them. Look for a pulled-out staple, a nicked wire, or a loose terminal at the powerhead, and check where the wire kinks behind the sensor bracket. If one LED is dead and cleaning/realignment changed nothing, damaged wiring is the next most likely culprit — repairable, but at that point most people prefer a technician with a meter.
When the sensor really has failed
Photo eyes do die — electronics age, coastal salt corrodes boards, and sun-baked housings crack. The tell: LEDs that stay dark or flicker with clean, aligned lenses and intact wiring, or a door that reverses intermittently at random (not at one repeatable spot — that's a track or force-setting problem instead). Replacement is quick and inexpensive as garage door repairs go: around $150–$300 fitted for a new pair, matched to your opener brand. We carry common pairs on the van, so it's a same-visit fix.
Don't bypass the sensors
Online forums are full of instructions for jumping the sensor terminals so the door closes without them. That removes the one system standing between a closing door and a child, pet or car boot. If the sensors are faulty, fix or replace them — a working pair costs less than a panel repair, let alone what the bypass risks.
Still stuck? If the LEDs are solid and the door still won't close, the fault has moved up the chain — force limits, logic board or a binding door. Our common problems guide covers the wider diagnosis, or book a repair and we'll sort it on-site.