Question about Sears Craftsman LiftMaster Chamberlain Garage Door Opener Wireless Keypad Model 976LM Security+

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Chamberlain Liftmaster bounces back up sometimes...

This is not a sensor problem. The motor pushes the door too far, the door hits the ground and rather than stopping the moving part of the garage door opener (I don't know what that part is called), that part keeps going, the bar along which is moving buckles a little and then the door starts opening and moves back to the fully open position. This happens about 30% of the time - seemingly random.

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On the side of the motor unit you will find the 'down limit control'. Using a small screwdriver turn this control in the opposite direction of the arrow printed on the cover. Some tweaking will most likely be necessary. You can remove the cover and watch the limit switch assembly and get a good idea how it works.

Posted on Sep 30, 2009

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1 Answer

My chamberlain liftmaster pro closes but then opens up on its own. the sensors are operating fine. what is the issue with it


If the main light flashes 10 times when the door reverses it is a door sensor problem. If the door is hitting the floor and reversing with no flashing of the lights it is caused by the door traveling too far. On the side of the motor unit you will find the 'down limit' control. Turn this a bit in the opposite direction of the arrow printed on the cover. Some tweaking of this control will probably be needed to get it just right.

Sep 04, 2011 | Sears Craftsman LiftMaster Chamberlain...

2 Answers

When the door closes, it automatically reopens. There are no obstructions so that isn't the issue. If I disconnect the door and cycle the automatic is closes and then immediately reopens.


make sure that the auto matic reverse circuit light is being read correctly. they is a light extending a beam of infared light, you can't see it, to a reflector across the garage at the floor level at the garage opening. There should be an indicator light, usually green and red. Line up the light and reflector until the green light comes on.

Mar 08, 2011 | liftmaster Chamberlain Garage Door Opener...

1 Answer

I just replaced the gear and sprocket assembly on my craftsman garage door opener. Now when I hit the remote the motor only moves the door about a foot and then reverses. Any suggestions?


Make sure you put the black cup back on the end of the motor shaft and that it is pressed all the way on. Make sure the RPM sensor is plugged in. If neither of these are the issue, then you probably did not have the motor shaft pushed all the way back when you tightened the coupler after replacing the worm gear. Loosen that coupler up and from the front of the motor (opposite end in which the coupler is on) push the shaft back as far as it will go. Hold it there while you tighten the coupler back up and then try it.

Dec 29, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Door goes down but continues to bounce back up


If the door reverses when it hits the floor it is traveling too far in the down direction. Locate the 'down limit' adjustment on the side of the motor unit. Turn this control in the opposite direction of the arrow printed on the cover. Some tweaking will be necessary to get it just right.

Oct 02, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Door closes to fast and sometimes re-opens by itself


A couple possibilities here. Make sure the door spring isn't broken. Your door is traveling too far in the down direction and when it hits the floor the safety sensor reverses it to the open position. The down limit adjustment is on the side of the motor unit.

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

1 Answer

Garage door bounces back open


It sounds like your door is traveling too far in the down direction. Locate the 'down limit' control on the side of the motor unit and turn this control in the opposite direction of the arrow printed on the cover. Some tweaking may be necessary.

May 13, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Liftmaster formula 1 garage door opener keeps "bouncing" open


If the door reverses when it hits the floor it is traveling too far. Locate the 'down limit' control on the side of the motor unit and turn this in the opposite direction of the arrow printed on the cover. Some tweaking will most likely be necessary. You can always recognize a sensor problem because the main light will flash 10 times. If the main light isn't flashing it isn't a sensor problem.

Sep 26, 2009 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

My liftmaster formula one has one sensor light green and the other yellow. no amount of realignment helps this. the garage door will bounce back up when it hits the bottom and won't stay shut. have tried...


One photo eye should be yellow and the other one green. The problem seems to be your down limit to be set too far. When you stand facing the door behind the operator the limit adjustments should be on the left hand side under the light cover. The down limit is the one closest to the door.

Sep 26, 2009 | Sears Craftsman LiftMaster Chamberlain...

2 Answers

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

Jul 03, 2009 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Sears Craftsman 3/4


Open up the caseand look at the travel assy. Sometimes the limit (up or down) do fall off the assy. Just snap it back on.

Jan 06, 2009 | Sears Craftsman LiftMaster Chamberlain...

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