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

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Garage door model#139.53400

Replaced the gears and sprocket now the door will go down ,but not up motor run only one way

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Should have a switch located that is tripped by the gear or sprocket that trips the reverse switch. May want to see what switch is not being triggered when all the way down.

Posted on Jan 14, 2009

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SOURCE: Garage door opener motor doesn't work.

2 flashes is a safety eye issue, but you problen is most likely that the chain is not sync with the limit setting. Take the bottom off the gear and sprocket assemble and rotate center limit srew until it is in the same position as the trolley.

Posted on Jan 30, 2009

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HI, AFTER REPLACEING PLASTIC GEARS IN SAERS GARAGE DOOR O[ENER, OPENER WILL NOT GO THROUGH COMPLETE CYCLE. WHEN BUTTON PUSHED TO OPEN, OPENER GOES INTO CLOSE CYCLE AND HITS STOP BOLT. ATTEMPTED TO ADJUST...


Loosen the chain enough so that you can remove it from the sprocket above the motor unit. With the door closed run the motor until the sprocket turns clockwise and stops. With everything attached replace and tighten the chain. Some adjusting of the up and down limits will probably be required.


Mar 28, 2011 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Hi The Garage Door motor runs when button is hit but the Opener Sprocket does not turn. Fixing suggestion is appreciated. Thanks Joe


It sounds like the nylon gears inside the motor unit are stripped. You might want to release the door and see if you can work it up & down easily by hand. The door lift springs may need adjusting to help the door move easily. You will need to remove the metal cover on the motor unit to see the gears and the internal components of the opener to verify the problem. It takes about 2 -3 hours and about $125 to replace those gears if you do it. I hope this helps. Please vote yes. Thank you.

Dec 07, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

My garage door chain came off, i put it back on


Loosen the chain enough so that you can remove it from the sprocket above the motor unit. With the door closed run the motor until the sprocket turns clockwise and stops. With everything attached replace and tighten the chain. Some adjusting of the up and down limits will probably be required.

The chain normally comes off when there is a problem with the sprocket and gear assembly. The bearing goes bad and lets the shaft lean towards the door and the chain comes off. If this happens again you will need to replace that assembly which is part #41C4220A and is available at any good door service company.


Jul 24, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

I replaced the sprocket and gear assembly on my


Here are some things to check.

Loosen the chain enough so that you can remove it from the sprocket above the motor unit. With the door closed run the motor until the sprocket turns clockwise and stops. With everything attached replace and tighten the chain. Some adjusting of the up and down limits will probably be required.

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.






Jan 16, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

The door only moves 15 inches in each direction. I just installed a new gear kit.


Loosen the chain enough so that you can remove the chain from the sprocket above the motor. Run the motor until the sprocket turns in the clockwise direction and stops. With the door in the closed position replace and tighten the spring. This will get everything in sync and you will most likely need to tweak the 'up and down limit' controls to get it just right.

Oct 14, 2009 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

I just replaced the gears in the opener and now the door stays open about 2 ft. When I hit the button it closes about 1 ft. and returns to it's original position...


Loosen and then remove the chain from the sprocket above the motor. Run the opener until the sprocket has turned in the counterclockwise and stopped. Now with the door in the open position replace the chain on the sprocket and tighten. This will get you close and minor adjustments to the up and down limits may be needed.

Jul 23, 2009 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Craftsman Garage Door Opener Model# 13953919 not working.


Yes replace the entire assembly. The part number is 41C4220A Sprocket and Gear Assembly and is available at Sears or any good door opener service company. It comes with instructions.

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

3 Answers

Motor runs but door does not open


you have a stripped gear on your opener. Replace gear and sprocket kit

Feb 01, 2009 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Garage door opener motor doesn't work.


2 flashes is a safety eye issue, but you problen is most likely that the chain is not sync with the limit setting. Take the bottom off the gear and sprocket assemble and rotate center limit srew until it is in the same position as the trolley.

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

2 Answers

Lift master garage door opener. Motor makes noise when switch is hit likes its running but chain/sprocket doesn't move and the door is stuck open. Chain is on sprocket. Not sure if the motor is frozen? ...


I had the same problem. Took the cover off of the opener and found that the gears were stripped on the unit. Motor was fine. You can order gear replacement kit for the unit. They are a plastic type sprocket and worm gears. The kit comes with spindles and all necessary clips. You have to take the unit off the ceiling to replace the gears, but the process if very easy to do. Parts kit about $40 on line, much cheaper than a new door opener. Total process took less than 2 hours, including getting the unit down and back up again.

Jan 24, 2009 | Sears Craftsman LiftMaster Chamberlain...

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