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The safety beam is the one part of a garage door designed to stop it working. When something breaks the beam, the door will not close, and if it is already closing it reverses. That is exactly what you want when a child, a dog or a bumper is in the opening. It is less welcome when the beam is tripping on nothing and you are standing in the rain holding the wall button. This guide reads the symptoms first, because the door tells you where the fault is before you touch anything.
What the door is telling you
- Opens normally, will not close from the remote or wall button, and the opener light flashes or the unit clicks: the beam is broken or the sensors cannot see each other. Nearly always alignment, dirt, glare or wiring.
- Closes only while you hold the wall button down: most openers allow a held-button close with the beam faulted, so this confirms the sensors, not the motor, are the problem.
- Starts closing, then reverses part way: something crossed the beam mid-travel, or a sensor is loose and shifting as the door vibrates. A door that reverses right at the floor is usually a force or travel-limit setting, not the sensors.
- Will not open either: not a sensor fault. The beams only govern closing. Start with our door won't open guide.
- One sensor's indicator light is off or blinking: the sensor is not powered, not aligned or not receiving. Steady lights on both units generally mean the pair is happy, though the colours used vary by brand.
About those LED colours
Manufacturers use different colours and blink patterns for sending, receiving and fault states, and some models have a light on only one of the two units. Treat a steady light as good and a dark or flashing light as the unit to investigate, then confirm the meaning in your opener's manual.
The five causes, in the order a technician checks them
1. Alignment
The sensors sit on brackets about fifteen centimetres off the floor, one each side, and they only need to be knocked a few degrees to lose each other. A bin, a bike wheel or a broom is enough. Look along the track: both lenses should face each other squarely at the same height. Loosen the bracket wing nut, nudge the sensor until its indicator goes steady, and tighten it again. Check the bracket itself is not bent.
2. Dirt, webs and moisture
Lenses at ankle height collect dust, spider webs and, after a storm, water droplets. Wipe both lenses with a soft dry cloth. Do not use solvent or anything abrasive; the lens is plastic. Perth's summer dust and spring spiders make this the most common cause we clear on a service visit.
3. Sunlight
A receiving sensor that faces west can be flooded by low afternoon sun and stop registering the beam. The tell is a door that misbehaves at the same time each day and works fine in the morning. Swapping the sender and receiver so the receiver faces away from the sun, or fitting a small shade hood over the lens, fixes it. Some brands sell a sun shield for exactly this.
4. Wiring
Two thin low-voltage wires run from each sensor back to the motor head, usually stapled along the wall. Look for a staple driven through the insulation, a wire chewed by a rodent, a loose terminal at the sensor or the motor, or corrosion where the wire was joined. A dark indicator light on one sensor with the other one lit points here. Repairing a low-voltage wire is safe to do with the opener unplugged, but if the terminals at the motor head are involved, leave them to a technician.
5. A failed sensor
Photo eyes do wear out, particularly on the sunny side, and a unit that stays dark with clean lenses, correct alignment and good wiring has most likely failed. Sensors are replaced as a matched pair from the opener's own brand, because the signalling is not universal between makers. Elite replaces or realigns safety beams for $150–$300, incl. GST, as part of garage door repairs across Perth.
A two-minute test before you call anyone
Sensor check
- Clear the opening. Move bins, boxes, hoses and anything within a hand's width of the door line.
- Wipe both lenses and look for steady indicator lights on both units.
- Wave a hand through the beam and watch the receiving unit's light blink off and on. If it does, the beam is live and aligned.
- Press close from the wall button. If the door now closes, the fault was one of the four physical causes above.
- If the door still refuses and both lights are steady, the fault may be at the motor head rather than the sensors. Our door won't close guide covers the limit and force settings that mimic a beam fault.
Never bypass the beam
Taping the sensors together, pointing them at each other on the wall, or wiring them out of the circuit turns a garage door into a moving weight with no way to stop. It also voids the point of the opener's safety reverse. If the sensors are faulty, replace them; do not defeat them.
Do the sensors need a reset?
There is no reset button on the sensors themselves. Cutting power to the opener for a minute clears some openers' fault memory and is harmless to try, but it does not fix alignment, dirt or wiring, which are the actual causes. If a power cycle appears to fix it and the fault returns within days, look again at the sun and the brackets. Our opener reset guide explains which resets exist and which faults they cure.
When to call a technician
Book a visit when both sensors are dark, when a wire is damaged near the motor head, when the door still will not close with clean, aligned, steadily lit sensors, or when the door reverses at the floor rather than mid-travel. That last one is a limit or force adjustment on the opener, which is a technician's setting, not an owner's. A garage door service includes a safety-beam test and alignment as standard, from $140 plus parts, incl. GST.