Garage door safety sensors: how they work and common faults

Garage door safety sensors are the small photo-eye units mounted near the floor on each side of the opening. They shine an invisible infrared beam across the doorway, and if anything breaks the beam while the door is closing, the door stops and reverses. This is why an automated door refuses to close, or reverses part-way: the beam is blocked, misaligned or faulty. Most sensor problems are quick, cheap fixes, and an opener or sensor repair in Adelaide runs $150 to $400 when a part is involved.

How safety sensors work

The 2 sensor units sit about 150mm off the ground, one each side of the door. One sends an infrared beam, the other receives it. While the beam is intact, the door is allowed to close. The instant something crosses it (a person, a pet, a bin, a reversing car), the beam breaks and the opener reverses the door to avoid a crush. They are a legal requirement on automated doors for exactly this reason, and any proper automation install includes them.

You can tell they are working by the small indicator LEDs on each unit: a steady light usually means the beam is aligned, a flashing or off light means it is blocked or misaligned.

The common faults and quick fixes

Most sensor problems fall into 4 buckets, and 3 of them you can often clear yourself.

• Something is in the beam. A bin, a stored item, cobwebs or leaves. Clear the doorway and try again.
• The lenses are dirty. Dust, spider webs or salt film (common in the coastal belt) block the beam. Wipe both lenses clean.
• The sensors are misaligned. A knock can twist a sensor so the beams no longer meet. Gently adjust until both LEDs go steady.
• A sensor or wire has failed. A dead sensor, a chewed wire or a surge-damaged board needs a specialist, a $150 to $400 repair.

If the door still will not close after clearing and realigning, the fault is electrical rather than a blocked beam. Work through why won't my garage door open and, if the motor is behaving oddly too, the signs in signs your garage door motor is failing.

Why Adelaide sensors fail when they do

Local conditions drive a lot of sensor call-outs. In the coastal salt-air belt (Semaphore, Henley Beach, Glenelg, Hallett Cove), a salt film builds on the lenses and corrodes the wiring, so sensors need cleaning more often and fail earlier. Across the whole metro, summer thunderstorm power surges damage the sensor circuitry and the opener board it connects to, so a door that suddenly reverses after a storm often has a surge-hit sensor or board. A surge-protected connection protects both.

Spiders are the other quiet culprit: Adelaide garages collect webs across the low-mounted sensors, which is one of the most common "my door won't close" causes and costs nothing to fix.

When to call a specialist

Call someone when the LEDs stay off or flashing after you have cleaned and realigned the sensors, when the wiring looks damaged or chewed, or when the door behaves erratically in a way that points past the sensors to the opener. These are typically $150 to $400 repairs, in line with other opener faults on our cost page, and you can get a related figure from the motor replacement cost estimator. Programming issues after a repair are covered in how to program a garage door remote.

Get sensor faults fixed properly

A blocked or misaligned sensor is a 2-minute fix, but a failed sensor, damaged wiring or storm-hit board needs the right parts and a proper test of the safety system. Never disable the sensors to force the door shut: they are what stops the door on a child or pet. Get matched with vetted Adelaide specialists free and compare 2 to 3 exact quotes.

Frequently asked questions

Why does my garage door reverse before it closes?

Almost always a safety sensor issue: the beam is blocked, the lenses are dirty, or the 2 sensors are misaligned. Clear the doorway, wipe both lenses, and adjust the sensors until their LEDs are steady. If it still reverses, a sensor or the opener board may have failed, a $150 to $400 repair.

Can I bypass the safety sensors to close the door?

You should not. The sensors stop the door crushing a person, pet or object, and disabling them is unsafe and defeats a legal requirement. If the sensors are faulty, fix or replace them rather than bypassing. A specialist can supply and fit new sensors and test the safety system.

My sensors stopped working after a storm. Why?

Adelaide's summer storms bring power surges that can damage the sensor circuitry or the opener's logic board they connect to. If cleaning and realigning does not help, the electronics likely took a surge. A specialist tests and repairs it for $150 to $400, and a surge-protected connection prevents a repeat.

Door won't close? Get matched with vetted Adelaide specialists free and compare exact quotes.