How Garage Door Sensors Work (Troubleshooting & Fixes)

Let’s look at how garage door sensors work and what to do if they are not working correctly.

The sensors generate a low-voltage infrared beam that completes the electrical circuit when the door is activatedGarage door sensors are safety devices that prevent the door from closing on people, pets, or objects in the doorway. The sensors are located above the floor at each side of the door opening. 

We also look at how to test that the sensors are working properly and do some troubleshooting and how to fix problems.

How Do I Know if My Garage Door Sensors Are Working?

Since January 1, 1993, residential automatic garage doors have required safety sensors to prevent the door from closing on a person or object. Sensors can reverse the direction of the closing door. If the beam is obstructed in any way, the door will open.

You can check the lights or test the sensors by obstructing the beam.

Check the Garage Door First

Close the door and pull the red emergency release cord. Lift the door by hand to see if your garage door springs work properly, and the door closes and opens smoothly. If it does not. The problems are in your garage tracks, rollers, or springs rather than on your opener or sensors.

Read all about garage door springs here and common garage door & opener problems here.

How Do I Test My Garage Door Sensors?

You can test the sensors with a cardboard box or something similar. Locate the sensors on both sides in the doorway. They are usually 2-6 inches from the ground.

Place the box in front of the sensors and try to close the garage door or place the box during the door is closing. Be careful !!

If the door reverses when the sensor beam is obstructed, your garage door opener is functioning correctly.

If the door closes on the box, there is something seriously wrong with the sensors !

Garage Door Sensor Troubleshooting

A common problem with a garage door is when the sensor moves out of alignment.

Because of the sensor locations, they are often bumped.

Check the following things. So you can determine what is wrong and can you fix it yourself or should you contact an expert.

Dirty lenses

Living in a dusty region or doing lots of woodwork or some other projects in your garage. The sensor lenses may be dirty or dusty. You can wipe the lenses with water and cloth or some mild cleaning product.

Damaged Wires

There may be wear and tear in the wires that connect the sensors and openers. Check the wires for old age, damage caused by weather, pest, or mechanical damage. Many times, the malfunction can be due to a loose connection or broken wire.

  • Check the wires to the photo-eyes first.
  • Second, replace the photo-eye if broken.
  • Last the garage door opener logic board.

What Color Should the Lights Be on Garage Door Sensors?

Manufacturers use different colors.

  • Photo eyes in sensors will usually have an emitter eye and a receiver eye opposite to each other.
  • Check if the led lights blink when closing the door.
  • Blinking/flickering or no lights indicate the sensors are not aligned.
  • When adjusting sensors. Watch the blinking of colors and intensity of color. Try to get the color bright.

Do Both Garage Door Sensors Need to Be Green?

Colors depend on the manufacturer.

Color of Lights per Manufacturer


Both Sears Craftsman and Liftmaster brands are manufactured by the Chamberlain.

With this manufacturer first:

Check the light bulb at the motor. Push the wall console for the door to close, and if it does not move and the light bulb blinks eight times, the photo eyes are broken or not aligned.


Colors are AMBER/YELLOW for transmitting eye (should always be lit)

and GREEN receiving eye (should be brightly lit)


Older sensors look like squares, and newer ones have a cylinder shape


Colors are RED transmitting eye ( should always be lit)

And RED receiving eye (solid color)


Older sensors are shallow and clear and newer rectangular and deeper.


Colors are GREEN for transmitting eye (solid color)

And RED for receiving eye (solid color)



Colors are GREEN for transmitting eye (solid color)

And RED for receiving eye (solid color)

Find Replacement Safety Sensors for Your Brand of Garage Door Opener From Amazon. (Genie,Liftmaster,Sears,Chamberlain,Craftsman,Linear, etc,

How to Adjust Garage Door Sensors

Before taking sensors out, try wiggling them into place.

  • Open wing nut and remove receiving sensor from the bracket
  • Point the sensor away till the light goes off and wait 10 seconds
  • Put the sensor back to the bracket, aligning sensors until led lights are solid and bright and not blinking.
  • Close the wing nut.

If sensors are showing no lights or flickering lights. Inspect the bracket of the sensors. If they are loose, try to tighten the screws and align the sensors again. If the sensors stop blinking and the door closes properly, you have fixed the problem.

Intense sunlight can obstruct the sensors too. If everything else works. Try blocking out the sun with pieces of cardboard in front of the sensor without blocking the beam.

Error Codes

Garage door opener motor units have error codes. Count the number of blinking lights in the opener and consult the user manual to troubleshoot the problem. Blinks can be something like four-times every 10 seconds.

  • One blink indicates the problem with sensor wires is not connected correctly.
  • Two blinks are indicating that the sensor wires are shorted.
  • Four blinks will show that the sensor eyes are not aligned properly. They need an adjustment.

If you are using newer chain-drive models or belt-drive models, you can check for the following indications.

  • One blink down and one blink up shows that wires are broken, or sensors are uninstalled
  • Two blinks down, and one blink up will indicate the used wires are reversed or shorted
  • 4 blinks down, and one blink up will reveal misalignment or obstructed sensor
  • 6 blinks down and 4 blinks up will indicate that sensors are misaligned or obstructed temporarily

How Long Do Garage Door Sensors Last?

About 10 years, depending on your garage usage and weather conditions.

Can Sensors Go Bad on Garage Door?

Yes. Sensors can break down or not operate properly. If there is no led light showing at all. Try adjusting sensors first. Then check the wiring or replace the sensors.

How Many Volts Should Garage Door Sensor Be?

There should be 5 volts D.C. coming to the sensors.

Can Garage Door Sensors Get Wet?

Maybe they accidentally were exposed to rain or sprinkler water. Dry them out. Check your garage door weather sealing all around the door.

How to Bypass Garage Door Sensors

Suppose your garage door sensors are malfunctioning, and the door won’t close. In that case, you can bypass them temporarily before you get them fixed.

  • It’s safest to disengage the sensors when the door is closed. Your garage door springs might not work correctly, and the door could come falling down dangerously.
  • If the door is stuck open and won’t close, pry it open with something sturdy that can handle the door weight.
  • Pull the red emergency release cord. Now you can open and close the door by hand.
  • If the door was stuck open. Ask a buddy to help you remove the objects that you placed keeping the door from falling. Another person can hold the door in position. Keep in mind some garage doors weigh very much! If springs are not working.
  • Get the sensors replaced or fixed.
  • Connect the emergency release Back to the motor unit.

How Do I Connect My Garage Door Sensors?

Are Garage Door Sensors Universal?

Some models are advertised to be universal.

Universal garage door opener safety sensors should work with all garage door opener’s major brands. (Paid Link)

Chamberlain, LiftMaster, Craftsman.

Both Sears Craftsman and Liftmaster brands are manufactured by the Chamberlain Group and are fully interchangeable. The new Photo eyes are compatible with the old photo eyes.

Are Garage Door Sensors Required?

The U.S. Federal Law UL 325 requires all garage doors to include safety mechanisms, such as garage door sensors.

How Much Does It Cost to Replace Garage Door Sensors?

Replacing sensors are around $85-$100 and professionally installed total cost around $180

The cost to fix malfunctioning sensors without replacing them is about $75-$85

Can You Run Garage Door Opener Without the Sensors?

No. If you move one of the sensors out of line, the opener will not work.

Disconnecting the garage door opener from the garage door will bypass the sensors.

Close the door and pull the red emergency release cord. Lift the door to see if your garage door springs work properly, and the door closes and opens smoothly. If it does not. The problems are in your garage tracks, rollers, or springs rather than on your opener or sensors.

Can You Add Safety Sensors to an Old Garage Door?

Newer sensors won’t work with very old openers. And if your opener is over 10-15 years old, it’s time to replace it.

What Wire Is Used for Garage Door Sensors?

Typically 22/2 bell wire is used. You can pick it up at any hardware store.

Are There Batteries in Garage Door Sensors?

Garage door sensors discussed in this article usually operate with fixed wiring.

There are other kinds of smart sensors that just tell if your garage door is open or closed or can open and close it. Those units have batteries.

If you can’t fix the problem with your sensors, you may prefer to disconnect your door opener’s power. This will prevent the garage door from being opened or closed altogether.

If you can do without using your garage until sensors are fixed, this is the safest option. Bypassing the sensors means the garage door will be able to close, even if something is in the way. If you’ve got small children or pets, that could be very dangerous. A garage door can cause severe injury or even death.

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