Question about liftmaster Chamberlain Garage Door Opener Transmitter 300MC

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I have the chamberlain garage door opener. the door will not shut. the door travels to about 8 inches above the floor and then reopens. the door is just over one year old and has worked well up until this time. I noticed that on the door sensor on the right hand side looking from inside the garage has a green light, the sensor on the left hand side is amber. any suggestions

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The sensor colors are correct. Try wiping the little eye sensors that point at each other for one thing and make sure there isn't something protruding from door that's coming into the patty of electric sensors.

Posted on Mar 14, 2011

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How to program my garage door opener #53985 have to remotes and a wall button. Door keeps wanting to reopen after closing. Fred Haul.


Your problem has nothing to do with programming. It is one of two problems. Either the door sensors are misaligned or the door is traveling too far in the down direction and when it hits the floor the safety reverses it to the open position.

Make sure the door sensors are pointed at one another and the small light on each one is lit and not flickering. Tweak them a bit.

The down limit adjustment is on the side of the motor unit. Turn it a bit in the opposite direction of the arrow printed on the cover.

Feb 21, 2011 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

The garage door closes and then the door reopens.


If the door is hitting the floor and then opening it is traveling to far. Locate the 'down limit' on the side of the motor unit and turn this control a bit in the opposite direction of the arrow printed on the cover. Some tweaking will probably be necessary.

If the main light is flashing 10 times and the door is reversing it is a door sensor problem. Make sure they are pointed at one another and the small light on each one is lit and not flickering. Tweak them a bit. If you cannot get both lights to come on you have a bad sensor.

Jan 06, 2011 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Garage door loses travel settings after a day or two.Door closes then reopens after hitting the floor.I made the proper travel adjustments on the side of the unit then after 1 or 2 days the door hits the...


I have been having almost the same problem. My up limit setting is changing. I intend to replace the limit switch assembly. I know of nothing else that can cause this problem.

Dec 31, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

I have Craftsman ½ HP Garage Door Opener Model 139.18458D. It reopens immediately after closing. Sometimes it works normally, and sometimes gives this problem. I have tried adjusting the close force,...


It sounds like the door is traveling too far in the down direction. When it hits the floor the safety causes it to reverse to the open position. You need to adjust the 'down limit' not the force.

Sep 06, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Genie auto garage door. closes then imediately re...


GET A COPY OF THE ADJUSTMENT INSTUCTIONS FROM THE GENIE WEB SITE - IT IS A SMALL AND SIMPLE ADJUSTMENT - BUT, IF YOU MESS IT UP THE DOOR WOULD BE UNSAFE.

May 20, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

How can I udjust garage door so that will close all the way down to the floor? Sears 41A43157 ? It came with the house - previous owner had no instruction manual. It was installed in 1993. Otherwise works...


look for 2 plastic screws, should be white in color. the screw on the left adjusts the down travel. there should be arrows pointing to which way to increase the travel(i think turning left for down). if you only need a few inches to reach the floor you should be able to adjust. if its way off there may not be enough adjustment. 1 full turn will move will door a couple inches so adjust a little at a time or you may overshoot. good luck

Apr 06, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Garage door goes up, but only travels about 12 inches and stops when it comes down


TRY HOLDING DOWN THE WALL BUTTON TO CLOSE THE DOOR.
IF IT WORKS THE PROBLEM IS IN THE SAFETY EYES.

IF THE DOOR TRUELY GOES A FOOT OR MORE AND THE ABOVE DOES NOT WORK - DISCONNECT THE DOOR FROM THE OPENER AND MAKE SURE IT WORKS SMOOTHLY - LUBE THE SPRING(S) ETC,
IF IT GOES UP AND DOWN WITHOUT TOO MUCH EFFORT ADJUST THE DOWN SENSITIVITY - NOTE: THIS IS A VERY SMALL ADJUSTMENT 1/8 TURN IS MORE THAN ENOUGH

IF YOU STILL HAVE PROBLEMS DOWNLOAD THE OWNERSMANUAL FROM LIFTMASTER.COM NAD READ THE TROUBLESHOOTING SECTION

HOPE THIS HELPS

Dec 20, 2009 | liftmaster Chamberlain Garage Door Opener...

1 Answer

My Chamberlain garage door opener only opens 8 inches.


Sounds like you have broken door springs or a bad drive gear. Take a good look at the springs and then remove the cover and look at the gear. It is white nylon and is just in front of the motor.

Sep 05, 2009 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Two identical Sears doors jump about 6 to 8 inches up when opener button pressed. Periodically doors will stop at that point, need to be closed and then reopened to operate properly. Have tried adjusting...


It sounds like the door springs may be mis-adjusted. Release the doors from the opener and try raising and lowering them manually. They should not try to rise on their own.

Jul 30, 2009 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Opener will not reverse


FIRST YOU NEED TO RESET THE CHAIN .

Unplug power
Release the door from the opener close the door manually. take the chain loose and slide the traveler down to reengage with the trolley. Plug in power, run the unit with chain off untill it completes a clockwise cycle and stops. reconnect the chain and set tension.

Adjust the chain tension.

If it still moves 6-8 inches and flashes 5 times. the problem is in the rpm sensor.

Full diagnostics are in the owners manual - FREE at
http://help.chamberlain.com/help/en-us/InstructionManuals

Oct 06, 2008 | Sears Craftsman LiftMaster Chamberlain...

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