Troubleshooting a Garage Door That Won’t Close

Published on By Champion Garage Door Repair

Are you having troubles with a garage door which simply will not close? If you’re sure that the mechanics (garage door springs, tracks, cables, etc) of the door are not damaged, it’s more than likely that you’re looking at faulty sensors being your issue. Garage door sensors use infrared beams of light to detect the presence of objects, a similar technology to that found in remote controls and burglar alarm systems. The garage door sensors are designed to detect the presence of a car or object (and not squash it!) but defective sensors could lead to your garage door refusing to close, as it believes that something is blocking its path.

Most garage door openers will blink 10 times if an issue like this occurs. 10 blinks signify that the safety sensors are likely blocked or out of alignment, or may have problems with their wiring. They could also just simply be defective.

Before we begin, let us just remind you to always take proper safety precautions when handling live electric wires!

Now without further ado, here are three steps for troubleshooting faulty safety sensors.

1. Look for an item blocking the sensors

Sometimes it really is that simple. A small object such as a stray bucket, child’s toy or paint can could be enough to block your sensors’ infrared beam and triggering the garage door opener safety feature. Remove any pesky items and see if the door now works as normal.

2. Nothing blocking the sensors? Check their alignment and error codes

Garage Door Sensors

Sending Sensor (on the left) Receiving Sensor (on the right)

Each sensor has an indicating light. The “sending” sensor has a yellow or orange LED light on it. This “sending” sensor transmits infrared light to the “receiving” sensor, which has a green light on it. The sending sensor’s yellow or orange LED light should always be visible, whereas the receiving sensor’s green or red light should only be visible when the sensors are aligned and unobstructed. Check that both these lights are on, assuming there are no objects blocking the path between them. If the green/orange LED (receiving) light is off, carefully adjust the receiving sensor until the it light reappears and stay solid. If the green/orange LED light reappears and stay solid, you have successfully realigned the sensors. Now try closing the garage door as normal. If it closes smoothly, your problem was simply misaligned garage door opener’s sensors!

Is one (or both) of these lights not coming on, even after you have tried to align them? In this case, you need to check your LED troubleshooting light on your garage door motor unit in order to diagnose the problem further. Look for an error code from the blinking lights on your motor unit. For a Liftmaster, Chamberlain or Craftsman garage door opener: if it is a single LED light, it will flash:

  • 1 blink if the sensor wires are disconnected
  • 2 blinks if the sensor wires have shorted
  • 4 blinks if the sensor eyes are slightly misaligned

On the other hand, if you have a unit with “up and down” arrows, they will blink in these orders to indicate the following errors:

  • 1 up blink, 1 down blink, this means that the sensors are not installed or their wires are broken in some way
  • 1 up blink, 2 down blinks, this means that the sensor wires have shorted or are reversed
  • 1 up blink, 4 down blinks, this means that you have an obstructed or misaligned sensor
  • 4 up blinks, 6 down blinks, this means that your sensors are temporarily obstructed or misaligned

If your error code indicates a problem with the wiring, check the wiring! Look for any damage or separations in the wires. Bear in mind that this may be difficult to trace a faulty wire, however, if your wiring is hidden away behind walls and crevices. Repair or replace any broken or damaged wires, and this will likely fix your problem.

It’s also worth checking your safety sensors’ wire connections on the motor unit, and reconnect any loose wires you find. The white wires should be twisted together, and should be connected to the white terminal. The black and white wires should be connected to the gray (colour may vary with each brand). Make sure that all the wires are connected properly and securely to their appropriate terminals.

Now, try to operate your garage door once more. Still no luck? Read on.

3. Test your safety sensors directly via the garage door motor unit

Testing your safety sensors directly via your motor unit allows you to ascertain whether you have defective sensors or a break in your wiring that isn’t visible.

First, remove the sending sensor (yellow/orange light) from its bracket. Disconnect or cut the sensor from the wire around 12 inches from the end. The sensor wire has 2 strands, carefully pull the strands apart. Then, with the appropriate tools, strip around half an inch of insulation off the end of each wire strand. After this, disconnect the existing sensor wire strands from the motor unit. Then, connect the short white wire strand to the white terminal of the motor unit, and connect the other strand to the gray terminal on the motor unit.

After this, check if the sending sensor’s yellow/orange LED light has turned on. If the sending sensor’s LED light remains off, then your sensors are defective and are in need of replacement.

Garage Door Opener Terminals

Garage Door Opener’s Terminals

However, if the yellow/orange light turns on, then your sending sensor is functioning normally, and the problem may lie with your receiving sensor. It’s now time to perform a similar test for the receiving sensor.

For the receiving sensor (green or red LED light) we’re going to repeat the first few steps. Disconnect or cut the sensor’s wires approximately 12 inches from the end, separate the 2 wire strands, and strip approximately half an inch of insulation from each strand. Now, disconnect the existing sensor wires from the motor unit terminals (the white and gray terminals we used earlier).

Now, with both sets of wires, twist together the white and black strands from BOTH the receiving and sending sensor wires. This will leave you with a “single wire” that is twisted together. Do the same for the remaining plain white strands from BOTH the receiving and sending sensors. You now have 2 “single wires” comprised of twisted together receiving and sending wires.

Connect the combined white wire strands into the white terminal on the motor unit, and connect the combined white & black wire strands into the gray terminal.

Now, hold the sensor lights together in such a way that they should both light up (i.e. their beam is aligned because they are right next to each other). If one or both of the green and yellow/orange lights do not turn on, replace your safety sensors; they are defective. However, if both lights do turn on, press your garage door remote as normal and see if the door closes as it should. If it does, your sensors are okay, and you simply have a fault with your wiring somewhere.

If you wish to replace the faulty wiring yourself, you need to make sure you buy the correct replacement wiring from the appropriate manufacturer. Simply connect your replacement wires to the appropriate motor unit terminals (white and gray), guide them along your chosen wire path carefully, and then connect them to the sensors. Make sure to align your sensors properly (so that both the green/orange and yellow/red lights are visible) and voila! Your garage door should now be back to normal, and should close as it normally would.

We hope you find this troubleshooting guide helpful. If none of our tips here worked for you, it may be worth trying troubleshooting common garage door issues, troubleshooting a garage door opener or simply hire professional garage door repair company to take a look!

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