20 Most Recent liftmaster Chamberlain Garage Door Opener Transmitter 300MC - Page 2 Questions & Answers

SORRY BUT THE GUY WHO GOT RID OF IT HAD THE RIGHT IDEA.
I DOUBT YOU CAN FIND A REMOTE AND IF IT HUMMS IT IS A POTENTIAL FIRE HAZARD.
SORRY I CAN'T GIVE YOU GOOD NEWS

Try connecting transformer to your other 115 volt line

Your answer is in the last line, unless you have those lights, the opener assumes something is in the way. Make sure you have the green one pointing in the direction of the local sunsets as this is also a problem certain days of the year.

CHECK TO SEE IF THE LED ON THE WALL BUTTON IS BLINKING - IF IT IS SOMEONE HAS PUSHED THE VACATION LOCK BUTTON.
PRESS THE LOCK BUTTON TO MAKE THE LED STAY CONSTANT AND IT IS FIXED.
HOPE THIS HELPS

this is likely a force setting issue, with all the humidity the door might be getting more stiff, on the back or side of the unit there should be a screw it adjust, or you can reference the manual, but before doing so you should release the door from the opener (handle on the trolley) and check to see just how stiff the door is, if the spring has broken you will have to get a door guy to fix it.

I would replace the battery anyway. Even with no use batteries drain over time. That's the easiest troubleshooting step and more than likely the problem. Once that's eliminated we can try harder solutions.

Hi,
There is a rope or string hanging down that releases the dog that hooks the door to the chain...if someone pulled that the door will not open. You need to pull down and back on the srting to relaese the dog and then push the door up to catch the chain...then the door will work again...

heatman101

One should be green and the other amber - The amber one stay on all the time, the green one tells if the alignment is OK or not (solid green means OK) Hope this helps, if it does please click 'helpful below'

Hi Laura: Mine does this too. I just thought that it was supposed to do this as it made sense to me. The light automatically turns off after a few minutes, so if the sensor indicates that someone is walking in and out while the door is open, the light stays on. I'm thinking........... It ain't broke..... don't fix it.

That is the quickest way to get one that works.

The most likely cause of this problem is that the door is unexpectedly hitting the ground before the shut off of the motor. It is possible that the door is also jamming which makes the unit think there is an obstruction. If there is no mechanical problem with the door itself, you can make adjustments to the up/down force and the up/down limits. These adjustments are at your lifter motor unit and you should check or download your particular manual. I have linked a video showing the basics for this adjustment.https://www.youtube.com/watch?v=GebkW96Sd_c

If it's just off a little you can adjust the limits. If it's off alot you need to take the gear set back out and set the belt / chain / screw to the closed position. run the operator to the closed position and then install the gear set.