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

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Sear 1/2 HP Garage door opener with replaced gears

I replaced the gears on both of our Sears 1/2 HP garage door openers. The first one works fine. With the second one when you try to run it all it does is run for a few seconds and then reverses. It does this whether or not the chain is hooked up to the sprocket. Is this a motor problem, a board problem or a wiring problem? I've tried adjusting the lift travel and force but nothing changes.

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  • Anonymous May 05, 2008

    I have the same problem after replacing the gears on my Sears 1/2 HP garage door opener. When I try to run it all it does is run for a few seconds and then reverses. It does this whether or not the chain is hooked up to the sprocket. Is there anyway to fix it? or is it time to buy a new Garage door opener:)

  • srcollins3 Aug 04, 2008

    Same problem. I replaced the Gear and Sprocket on a Sears 1/2 HP, model# 139.53515SR garage door opener. When the the opener button is pushed the door travels down a few inches, then reverses direction. I've tried adjusting the limits and the force. No difference. I don't think this could be sensors as this happens with the chain attached and without the chain attached... Any suggestions would be appreciated! I

  • wildbregner Dec 30, 2008

    Same exact deal with mine.

  • bsam420 Jan 08, 2009

    I have the same exact problem

  • sds02 May 11, 2010

    Have you checked to see if the garage door will reverse when it hits something while closing? This is a safety feature that must be checked.

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The actual problem is after power on the opener, its initial state is uncertain. It may be in ready to close or ready to open state.

If the garage door is in closed position, likely the opener will still try to close it, because its initial state is uncertain. That's why you guys see it travels 2 seconds and reverse.

In order to fix this problem, after you power on the opener, do NOT hook up the chain, and do NOT mount the sprocket cap(so you can see the sprocket travel direction). While you watch carefully at the sprocket, press trigger button on remote control or ask someone press wall control button. Make sure the sprocket turns clockwise and stop. If the sprocket turns counterclockwise, press the control button again, so it will turn clockwise. Let it finish clockwise turn. At this moment, the opener is in ready to open state.

Cover sprocket cap and hook up chain. Mount door bracket and adjust. Your door must be in close position.

You are ready to go.


Posted on Mar 07, 2009

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Ive had the same problem many times. i ve checked for solutions and found that the rpm sensor is to far out and this causes the reversal after a few seconds of running tried the recommended solution yeaterday losen set ring and it lets the wheel come further down to the sensor . but this did not fully solve my problem so i replaced it with a new opener. just finished tinkering with the old one and found the solution. the motor had to much end play and was letting the wheel move out of sensor range.

took old set ring and washer and placed it on other end of shaft and low and behold it worked.

ive got four others of these and some had more end play than others so the first solution worked on some and the others which ad nearly 3/4" end play i had to used the latter method of putting a washer and set ring on note the washer acts as a buffer between theset ring and motor bearing.

Posted on Jan 10, 2009

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I had the same problem. After reading all these suggestions and nothing worked, I realized there was a black cap on the end of the shaft coming from the motor near the circuit board. The rim of the cap went thru a sensor on the white plastic board with all the travel screws. It was almost off. I pushed it back on and it worked. It must activate something in the board.

Posted on Feb 28, 2013

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All this is over my head!

Posted on Feb 09, 2013

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THANKS Daviddeigns!! After I read your solution I KNEW that was my problem. Initially my door was working after gear replacement. However, it sounded like it the motor was straining so I adjusted the locking collar on the motor shaft so there would be less pressure against the bellville washer. Of course once I did this the door started reversing itself after moving 12" or so. Obviously by loosening the locking collar the rpm cap had moved out of the rpm sensor range. Made perfect sense once I read your post. 
This seems like a VERY common problem based on the number of posts on this site of people who have the same problem. Folks, if your door is reversing itself after 12" or so  adjust the locking collar so that it is tightened down after you take all the shaft play out by pulling the shaft towards the circuit board then cranking down on the collar. If you still have problems I'd suggest experimenting with the rpm cap by sliding it up or down the shaft.
All this above assumes that you've got the rpm sensor plugged in and there are no other issus.

Posted on Mar 21, 2009

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