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

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Replaced sprocket and worm gear on chamberlain 1/2 opener

I replaced the sprocket & worm gear on my Liftmaster 1255 and it only raise 6 inches & reverses automatically and stays open 2 inches. Green light blinks 5 times...no limit or force adjustments make a difference? I'm stuck....

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The motor shaft may not be pushed in all the way. Check to see if the motor shaft is sticking out past the end of the motor more than about 1/2". If so, then remove the black cup on the other end of the motor shaft and then losten the two set screws holding on the collar. Then push the motor shaft all the way in toward the circuit board and then tighten the collar back on. The shaft has to be all the way forward to allow all the travel the gears need to take the trolley completely back and forth.

Posted on Feb 05, 2012

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CHECK THE RPM SENSOR A LITTLE CUP ON THE MOTOR SHAFT. IF IT IS NOT INSTALLED SO THAT IT INTERUPTS THE SENSOR THE OPENER WILL GO 6-8 INCHES AND STOP.(AND BLINK 5 TIMES)

ONCE YOU GET THE LITTLE WHITE CUP PROPERLY ALIGNED YOU WILL NEED TO RESET YOUR TRAVEL LIMITS AND TEST YOUR REVERSE / SENSITIVITY SETTINGS.

HOPE THIS HELPS

Posted on May 28, 2010

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Check the plastic cap between the rpm sensors run freely

Posted on Mar 10, 2009

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Sears Craftsman LiftMaster Chamberlain Garage 13953664SRT worm gear stripped who do I replace it


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Is there any adjustment for the gear drive sprocket that meshes with the worm drive? my gear is not engaging any more


If your drive gear is not meshing with the worm gear it is because it is worn out. You'll need to replace it post haste. The part number is 41A2817 and is available at Sears or any good door opener service company.

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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.






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1 Answer

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2 Answers

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I have a 1265 and took the cover off (unplug first).
There are screws securing the cover: 2 on each side at top, 2 at either end bottom.
Then I disconnected the chain.
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Then at the bottom of the shaft is the "limit switch assembly" that is clipped into the metal housing. Squeeze the 2 on the outside and it should swing free.
Then at the very end of the shaft there is another plastic gear. It is secured by a 3 prong plastic clip. Pull the outside clips away from the shaft while pushing the center piece back through the shaft. The gear should come off and you can now remove the gear and sprocket assembly up through the assembly.
call 800 528 2817 and order the "Gear and Sprocket Assembly".
I am waiting for the part and assume we reverse the order above to reinstall.

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readjust the sensor controls on the side of the unit

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