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

2 Answers

Replaced gears, now only moves about 3 feet

My opener was acting up then"froze". I opened it up and saw the gears were shot (white plastic snow everywhere and worn down gear), I replaced the gears and now it moves, however, it only moves about 3 feet then reverses. It does not even go far enough to hit the up/down settings/sensors. I have unplugged it, played with tension, up/down settings etc with no success. Thoughts?

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  • Tim32 Feb 07, 2008

    I actualy have the door unhooked and yes, the door itself opens and closes fine so no rail issues. Tension adjustments won't matter if door is not locked on right or should I hook door back up? As for limit adjusters the door (the thing the door locks onto) is stuck in a 3 foot path between the stops, meaning it does not reach the up sensor or return to the down sensor. Just moves very slightly in the open space between them...

  • Ed_flyfish Feb 11, 2008

    I have the same problem, but I already have the rpm sensor in place. Could the rpm sensor be bad? I unplugged the circuit and had the same results. I removed the chain and limit sections as well. I also tried to adjust the tension to both extermes without success.

  • Ed_flyfish Feb 11, 2008

    My earlier comment asked if the rpm sensor was bad. I have the end cap in place. I was not implying that the end cap was the sensor, but the eye that it passes through. Could it also be a sensor alighment problem?

  • rubbishman Mar 01, 2008

    The top gear that drives the chain broke off of the opener, so I replaced it with the new gears. Now when I try to open the garage door it only moves maybe 7". Itryed to set the force and limmit switch with no effect. Is there some sort of way to reset the opener?


2 Answers

Fixed it earlier tody...I hate to admit it but I forgot to put the RPM sensor back on the end cap...(actually, I put it on the otherside of the motor)...nice move huh?

Posted on Feb 07, 2008

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  • 163 Answers

Look for a screw adjustment for the ammt of load it will accept.. Generally a screw adjust on the back.. Providing its not binding. If you release will it open by hand normally? Some also have up/down limit adjustments and maybe the gears werent timed right to coincide after they got chewed up..

Posted on Feb 07, 2008

  • Ken LaDere Feb 07, 2008

    Sounds like the gears are not timed with the rest.. Or there could be excessive force on the drive chain you cannot see.. Unhook this as well or look for an obstructed link/Bad drive gear tooth. Somthings hitting a block period)..(Turn down force adjust so as not to damage new gears)..There is a way to Zero all of it and it should be ok..

    (Why do I get myself into these)? because I like to fix everything...

    Good luck bud!

  • Ken LaDere Feb 09, 2008

    Hey.. Things happen..



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