Garage Door Safety Sensors Overview

I put this guide together to help my customers solve what is, by far, the most common problem with residential garage door systems — failure to close (FTC) due to an interruption of the Infrared (IR) Safety Sensors.

Also commonly called “photoelectric sensors“, “safety eyes”, “sensors”, “photo eyes”, and a bunch of other names (I usually go with “safety eyes” or “safety sensors”), these are the little electronic devices that are supposed to be near the bottom corners of your garage door. 

Their job is to prevent your garage door from crushing someone or something.  Most people never think about them — until they can’t get their garage door to close.

If that describes you at this moment, you can jump straight to instructions for overriding your garage door safety eyes so you can get on with your life.  But be sure to come back when you have time and figure out how to fix them for good.

History

People and pets used to get crushed by garage doors with alarming frequency.  Old garage door openers without safety sensors can be very dangerous, especially models that don’t easily reverse when they encounter an obstruction.  No person has been killed by a garage door opener with properly installed safety sensors since they became mandatory.  And far fewer pets have been killed and injured than in the old days, but there are still risks for them, particularly cats.

All garage door openers manufactured for sale in the USA since 1993 have been required to come with IR safety sensors.  Along with your garage door opener’s pressure sensitivity, they provide redundant entrapment protection in compliance with code UL 325. 

How Safety Sensors Work

Many people assume that because they are an electronic device the eyes are complicated, but they are not.  The safety sensors are technically part of the garage door opener (as opposed to the garage door itself), and come as a pair, made up of a “sending” and “receiving” side which do exactly what it sounds like they would.  If the IR (infrared) signal between the two eyes is interrupted while your garage door is closing, or there is a loss of power to one or both sensors, it will reverse to the open position.  If the door is already open and the signal is interrupted, it won’t close.

Safety sensors are powered by the garage door opener head (which houses the motor, circuit boards, and other parts) and are connected to it by low-voltage wiring (don’t worry it won’t shock you or start a fire).  The wiring may be hidden in the wall or stapled to the outside.

There are several wiring configurations that we will cover in another post that can affect how you go about troubleshooting your safety sensor problems.  If you have tried everything and can’t even get the sending eye to light up, this could be where the answer lies.

Your opener’s safety sensors have no impact whatsoever on your garage door opening.  If your garage door won’t open, don’t bother messing with the eyes, it is something else.  You could blow them away with a shotgun and the door would still open the next time you click the remote.  But closing your door would be a different story — safety sensors are designed to “fail safe” which means you can’t just disconnect or disable them and continue using your garage door opener as usual.

Luckily, there is a way to override the safety sensors so you can get your door closed in a pinch.

The IR signal that is being sent can be thought of as invisible light and the sending side as a small flashlight.  The further apart the eyes are, the wider but also more diffuse the beam is at the receiving eye. Things like dust, spider webs, and direct sunlight are more likely to interfere when the sensors aren’t well lined up.

There is usually about 10-15 degrees of wiggle room (this is my guess based on years of experience not a scientific measurement or specification).  I point this out because lots of people imagine that the signal is like a laser beam that shoots straight across and is very precise, but it’s not.  There is no need to get out a tape measure or leveling line, instead follow my procedure for lining up garage door sensors.

Some manufacturers (most notably Chamberlain/LiftMaster/Craftmsan) use safety eyes that are “polar”.  This means that there is only one way to connect the wiring to the opener or it won’t work, and you must keep track of which wire is which.  “Non-polar” eyes (Genie and Linear) are much easier to troubleshoot and deal with—it will work just fine even in you have the wires reversed.  Polar vs Non-polar is a topic that I will cover in detail in its own post.

New garage door openers come with a set of brackets that are used to mount the safety sensors.  Each brand has its pros and cons when it comes to mounting and alignment. The two most popular garage door opener manufacturers both use ridiculous designs, which make them way more difficult to install and deal with than they need to be. 

Because of all the brand specific quirks, I have separate posts to cover the most common models from the biggest manufacturers.  If you are having trouble with your safety sensors and you think it is more than a simple alignment issue, start here.  I have grouped together the different brands by parent company/manufacturer.

We are always happy to send a technician out, but lots of people could save time, the cost of a service charge, and major headaches by reading through this guide.