Why aren't my garage door remotes working?

Question

I have a Liftmaster 1/2HP garage door. For the past couple of months, the remotes have been getting less and less reliable. Now, they won't open or close the door at all. I've looked at multiple posts here and on YouTube but can't find an exact match for my problem. Here are my notes so far:

1. The wall-mounted button opens and closes the garage door 100% of the time. This suggests the garage door functions as it should.
2. The amber LED on the sensor is always-on. If I wave my hand in front of the receiving sensor, the green LED on the receiving sensor goes off (and will start blinking), as expected. This suggests to me that the sensors are correctly aligned.
3. The first remote is a third party remote bought of Amazon that has worked for a couple of years. I've changed out the battery.
4. The second remote is built into my Honda and has also worked reliably for a couple of years until recently.
5. I've unplugged the garage door opener and plugged it back in.
6. When I press the button on the remote, I see the "code" LED on the back of the garage door unit flash, suggesting to me that a signal is being received. Nothing else happens.
7. I have followed the instructions on the unit to erase all codes.
8. When I follow the instructions to re-program the codes (press the remote button, then the code button), the code LED on the back of the unit is solid, then flashes, but nothing else happens. The instructions indicate that the light bulb (not the code LED) of the unit should flash when programming is complete, but this never happens.
9. I've heard that light bulbs can cause RF interference, so I replaced the CFL bulb with a Genie-brand universal garage door light bulb.
10. I have a purple learn button

At this point in the troubleshooting I imagine that I've erased the codes, but seemingly it will now not re-program. The door mechanics work, the sensors seem to work and are unobstructed, the wall button works, the antenna seems to be receiving a signal from the remotes, but ultimately the remotes do not work.

What else should I be looking at, and why?

Answer 1

On the universal remotes, there's a confusing step where you actually hold the remote button until the receiver responds to it. I think it cycles through a bunch of different signal versions and you're supposed to let go of the button when it finds the compatible signal.

Answer 2

Unfortunately garage door openers operate on a relatively unregulated band of frequencies, the 300Mhz band. Since multiple remotes failed at once there's really only two possibilities here. Either: your garage door opener's electronics have failed in a way that means they are no longer receiving a signal, or: there is now interference on this frequency band.

The interference may be coming from a device in your home. If you want to troubleshoot interference from your home, you could shut down any battery powered devices that you can think of, particularly anything wireless, and then turn off all the circuit breakers in your house except the garage door opener. See if it works with the remote at that point. If it does, start turning on breakers until it stops working. When you find the one that starts causing problems, you can hunt for the device on that frequency band which is causing you an issue.

If it doesn't work, take your remote to a friend's house and add it to their garage door opener. If the remote works at their house, you're now down to either the electronics on the garage door opener being faulty, or interference coming from a nearby source such as a neighbor. Without sensitive equipment to look for the interference, at that point your best bet is to replace the opener.