Question about liftmaster Chamberlain Garage Door Opener Transmitter 300MC

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Door goes up ok, but will only go down a bit then stops...

Called the repair guys, they said to check the light sensors at the bottom of the doorframe for cobwebs/dust...did that and it worked. Ran the door up and down about 5 times, worked like a charm. Then on 6th time, it stopped half way down. Called the repair guys again, they said that doors are not designed to run up and down so many times so quickly. That it has a safety mechanism that stops it before it seriously overheats. Said to wait about 30 minutes for it to cool-off/reset itself. Am now waiting 30 minutes. That make sense to you?

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What the repair guys told you is true.

Posted on Jul 13, 2009

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Posted on Jan 02, 2017

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Lift master 1/2 hp door not closing...moves a foot and then stops and goes back...eyes are good, both lights solid...have messed with the force to see if that helps...and nothing...light on opener itself...


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Hi I have a Chamberlain garage door system. I use the remote to shut the door. The door goes down to a foot off the ground and goes back up again. I've tried for over an hour to get it to shut and it won't...


The motor has probably been shut off by the thermal protector. Wait 15 to 20 minutes and it will reset itself.

If when the door reverses and goes back up, the main light flashes 10 times 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.

Feb 18, 2011 | Sears Craftsman LiftMaster Chamberlain...

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I have a chamberlain liftmaster professional Formula 1 Garage door opener that has been working for 5 years. Now will not go down unless you hold the main button. Sensors blink when it hits within 3...


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1 Answer

Door goes up just past eye and stops. If I hold button down will go up all the way. Must hold button down for down position also or stops every couple feet.


Check your door springs and also remove the cover and check the drive gear. It is a white nylon gear just in front of the motor and may be stripped. You need to check your door sensors also. 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 necessary.

Mar 08, 2010 | Sears Craftsman LiftMaster Chamberlain...

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I have sears opener #139.53989. Every once in a while I have a down problem. It goes down within an inch of the floor and reverses. Sometimes I can hold the wired remote button and it will go all the way...


If the main light flashes 10 times when the door reverses it is a sensor problem. Check them very closely. If they are just a little off one of them will be flickering but it is difficult to see. This can also cause the problem to be intermittent. Tweak them just a little.

It is normal for that light to blink randomly.

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Door hit bottom and goes back up. one sensor light is green and


your door must have a pressure switch, and it is hitting the floor before the motor stops.

with the door topped out, release the lock and push the door closer to the motor and relock.

have a helper present to be safe

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Door will only close when held down


sounds like the gear drive is getting worn.
also make sure the track are free of any debris.

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