Sounds like you may have a short in your low voltage wire leading to the green sensor.

Did you install your own machine? Is your garage pre-wired (behind the sheet rock) or is the low voltage wire surface mounted?

I would check to make sure that a staple used during installation did not puncture the protective coating on the wire leading to the Green sensor light. This would cause a short and result in the problem which you have described.

Let me know if you have any questions.

Hold off on replacing the other sensor until you check the wiring.

You may have not needed a new sensor unit in the first place. If that is the case, perhaps the company you bought the unit from will allow you to return the unit.

Locate your service panel on your machine. This is the area where the force adjustments (2 blue dials with up/down arrows) and "learn button" are. If you don't know where this area is located, it is generally at the back of the motor unit exposed, under the white plastic lens cover, or on the side of the machine (either exposed or under a plastic flap that may read "service center" or "service bay" on it).

Next to the learn button there should be an orange or amber colored L.E.D. indicator light.

Is your light flashing at all? If so, please count how many times it is flashing.

(1) single flash every 10-15 seconds indicates that the infra-reds are totally misaligned or the wire leading to the infra-reds is open

(2) flashes every 10-15 seconds indicates the wire is shorted or the black/white wire is reversed

Thanks Sierra --
I now ran a new test line directly to the sensor terminal on the motor unit, to the new Receiving sensor, [green L.E.D.] while holding by hand, I lined up Green L.E.D.
sensor with Amber L.E.D. -- no luck. The new receiving sensor [green L.E.D.] does not lite. As before, Amber sensor is lit. I think this rules out any break or short in the line. Where do I go from here? Thanks for your suggestions

Hmmmm.......The only thing I can think of is that the black/white wires that connect at the terminal head (motor unit) may be reversed.

Did you check the LED indicator light that is next to the Learn Button????

Just curious, did you purchase Chamberlain brand sensors or some other brand or "universal" product? My experience is that one brand is not compatible with another (Chamberlain/Genie, Wayne Dalton/Linear, Overhead/Chamberlain) and that off-brand "universal" products rarely ever work.

There are several different generations of sensors.

1. Small plug-in jacks (similar to a telephone)
2. Hard-wired
3. Two screws that you loosen, strip one end of each wire, wrap it around the terminals, and tighten the screws down

The generation of sensor should not affect the function of your door, however, how did the low voltage wire connect at the terminal? If you had to strip the end of the wire and push it into the back of the terminal, perhaps you switched the two by mistake when installing the new sensor (an extremely common mistake).

> I was real careful not to reverse the b&w wires on either end.

> The LED light next to the Learn Button works.

> The new sensor is a Chamberlain brand.

> I had to strip the wire and push them into the terminal-- Iwas really careful not to make the mistake of switching wires. I've done that before.

Early on it was suggested that maybe that the Logic Board is bad. Any thoughts about that?

Thanks again for your suggestions. lou13

Ok, you say the LED next to the learn button works, but you didn't say if it was flashing or not.

If it is flashing, please count the number of flashes.

(6) Flashes would indicate that there is a motor circuit failure and Chamberlain would recommend that you replace the RX/LX board.

Before spending that kind of money, attempt to unplug the machine, wait 10 seconds, plug it back in and see if the LED light on the motor head has stops flashing or if the blink count has changed.

A faulty board is not a super-common problem, but it does happen. However, if your machine is only 2 years old, I would be very surprised if both your infra-reds and circuit board failed. If that really is the case, call Chamberlain and discuss the issue with them. They are an extremely good company and the only garage door opener manufacturer backed by the Good Housekeeping Seal.

The LED light next to the learn button does flash. It flashes once [1] and repeats again about every 7-8 seconds.

When I unplug the machine, wait 10 seconds, plug it back in, the LED light flashes 4 times once, and then goes back to one [1] flash about every 7-8 seconds. ?????????????

Thanks, Lou

Random flashing of this LED is normal.

Random flashing does occur. The LED indicator light is not a fool proof system for diagnosing problems, but it does provide some insight as to the issues at hand.

Sounds like you are still having issues with the infra-red sensors

(1) Flash - protector system wire open or totally misaligned
(4) Flashes - Infra-red sensor slightly mis-aligned (dim or flashing LED).

Have you tried Don's original suggestion of replacing the other sensor???

Sorry Don and Sierra, if I followed Don's advise from day one,I would have saved us all grief.

I replaced the other sensor - BINGO it WORKS.

My logic was that that if the other original sensors LED [amber] light was lite, it must be working. WRONG. So much for my logic.

Thanks Sierra for reminding me about Don's original suggestion.

Again thanks to all, Lou

Had the same problem after left garage door open during much rain.
Green sensor random flashing.
Was ready to replace sensors.
On the third day, my sensor "resurrected" and now works fine !
I guess something got wet and took 3 days to dry up inside.
So if your sensors get wet and stop working, allow a few days before you replace them and you may save yourself time and expense.

hey- I am a garage door technician, own my own company here in Ventura County- LA area. If you guy have questions that need answers or need any help let me know.

Kyle

Garage door will not close when morning sun is shining on the west safety sensor. Must block sun light to get door closer to make the door close.

Is this a typical problem? Are there filters that can be put on the safety lights and not block the two lights from seeing each other?

Thanks
Bob

Either move the sensors back away from the sunlight or use something like the cardboard roll from a roll of toilet tissue to shade the lens.

The garage door wont go up it just makes the sound and goes up a couple of inches also the sensors are green and the other one is red....the red sensor flashes when I put my hand infront while the green remains green and wont flash at all. What could be the problen and what can I do about it?

Remove the cover from the motor unit and check the drive gear. It is a white nylon gear just in front of the motor and it will be obvious if it is bad. The part number is 41A2817 and it comes with instructions.

HI All. Have a Chamberlain garage door opener doing the same thing. Thought it might help if someone would furnish the voltage across the connections at the motor. Across the red & white I get around 24v dc. Across the grey & white I only get .816. That's point 816 dc. Is that right? Thanks, Steve

Why don't you just tell us what your problem is and we will tell you how to fix it. Or come close.

No lights on the sensors. The door opens fine. To get it to close I have to push and hold button till it's all the way down. That's true with the remote or the wall mounted button. If I let up, no matter where, the door reverses and opens. I get one blink on the light next to the learn button. Anything else? Thanks, Steve

Skinned wires at sensors then pulled them out of motor, wrapped them together tested and had continuity where I skinned them at sensors. Put everything back together and still the same thing. That's why I wondered about voltages to see if I had a bad board. Thanks again

The 24volts between the red and white wire is correct. Check for 5vdc between terminals 2 and 3 on the rear of the motor unit. If there is no voltage or if it is greater than 6 vdc the logic board is bad.

Thanks Don. Really appreciate the info. give it a try today.

I was wondering if there was any problems with the remotes, possibly low battery levels or if the sensor was faulty. However if you have gotten new remotes, I am stumped as to where the problem could lie. I doubt I will be of much help.

I had the same people as others on this forum. After rerunning wire and seeing my new replaced sensor still flickering, I came here. Turns out the fix was also the other sensor. Thanks for those that gave the advice!

Hi All,
I just got a new Chamberlain Whisper Belt Drive 3/4 HP garage door opener. Installation was not that hard. But I found that the green LED light safety sensor does not light up at all while the amber LED light safety sensor lit up constantly. I have checked the voltage across the white and grey terminals which reads 5.94 V and I think it is good. I have also checked all the cable straps to make sure no short circuiting.
Following from other forum member, I have also checked the diagnostic LED light around the learn button but found it never lit up.
So am I so bad luck that I just got a busted green LED safety sensor?

Thank you in advance for your time to read my sensor problem and any help is appreciated.

To wonginlok:

Try reversing the connection (the wires) from the sensor to the motor/control board. Each sensor wire has to be connected to the correct wire going to the board. If one doesn't pay attention to that, one has a 50% chance of getting it right. Don't ask how I know!

My Chamberlrage garage door opener that replaced an older 1997 liftmaster seems to operating incorrectly.
When I adjust the the door up and down the units buttons are reversed.. the up makes the door go down and the down button makes the garage door go up. Not really a big deal unit you consider the protection system. It works in reverse as well . Instead of the door going up when it detects an obstruction .. it goes down .. My wife thinks that my installation is wrong .. any help?

Hello all,

I am having the same issue with my garage door. It is a chamberlain liftmaster and upon closing the door, it will retract and the light will start to blink. i noticed the sensor with the orange light is very dim and the other sensor with the green light is out completely. i tried repositioning them, but neither light ever got any better (green stayed out and the orange remained very dim).

My wife did give our garage a good scrubbing with the hose the other day and i read an earlier post that the sensors can get wet and need to be dried and may start working again. Other than that, does anyone have a clue to why the green sensor is completely unlit? How would i check for a short in the wires as they are hidden behind the drywall?

Thank you in advance,

TJ

Hi there

We have a Chamberlain ML750. It's been installed for around a year and I just noticed today that the yellow led keeps flashing. The garage door can be opened or closed without any problem. Anything wrong or it is just normal?

I have a craftsman garage door - both sensor lights are out, the main light flashes 10 times and the light by the learn button twice. I tried to reset it (unplugged it) still did not work. I did power wash the door and that is when it stopped working. The opener that is wired to the door does work. Any suggestions

I am having the exact same problem. No light on either sensor. Did you find a solution?

Hello all, I found this thread and was hoping you guys could help me out. The city had a planned power outage a couple of days ago...no issues up until then. When the power came back on the sensors were not lit. Had to manually open/close. Then out of nowhere the sensors had a steady light the next day. Garage opened and closed just fine.

Problem is that the sensors seem to stop working intermittently now. After they came back on, the remote/wall panel opened and closed just fine. A few hours later, my wife opened the garage, and when trying to close, it wouldn't.

Sensors are back off again...I've already adjusted the sensors, so I'm kind of stumped as to what I may need to do. Not sure why this problem never happened prior to the power outage either...

Any help would be appreciated!

safety sensor Problem could be occur because of a poor connection, incorrectly connected wires, or a short in the wire. Have you checked all these?

For what it's worth, here's my story. I replaced a sensor because it just stopped working one day (15 years old - green light side). I reversed the wires the first time installing (the wires were so old that I the black markings on the wire had faded away so I couldn't rematch them properly), but it was obvious I made the mistake because it caused the yellow light on the other sensor to stop working. After fixing the wire both yellow and green sensors lit up correctly, but the garage door would still not lower, even after unplugging and re-plugging in the main device. The next day I was ready to replace the other other (yellow light) sensor to see if mis-matched sensors may have been the issue, but the garage door closed without any issues! Apparently, the sensor just needed time to reset itself after installation. Not sure how long you need to wait, but it's at least five minutes and may be fifteen minutes or more.

I have a liftmaster and we replaced the sensors. The yellow light stays on and the green light is solid however when we lower the door the green light goes off and will not sense any objects under the garage. Any one know why that could be?

Just because they are new, doesn't mean one or two aren't defective. About 5 years after install our door would periodically retract after closing and flash the light on the opener. After fussing around with the sensors, I found that gently tapping on the right side one would allow the door to stay closed. After I got tired of doing that I ordered a set from Amazon and replaced the original sensors, I have not have any problems since..

Thanks to this thread, I saved myself a garage door repair call. I also thought that my problem was only with the green sensor since it would not light and the amber sensor was dimly lit. However, after I replaced both, the LEDs glowed brightly and the garage door functioned.

I just replaced the safety sensors due to the door not closing. It still isn't working and I don't think it's crossed wires. I replaced the wires as well just in case, careful to match the correct wires. I get a fast blink on both sensors that don't go off. The opener indicator on the rear panel will flash green intermittently. Any suggestions?

We tried to install safety sensors to our old garage doors Mastercraft from 1991. Can’t make them work.
Any suggestions?