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

2 Answers

Door opens and then closes wright away

I just changed the gears in the craftsman 1/2 horsepower opener and when I tried for the first time the door opens 2 feet and then closes right away.I tried all the adjustment screws and nothing seems to be working.Can someone please help.Thanks

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  • lawnofficer Feb 27, 2009

    The main drive gear was stripped so I got a kit and replaced it, now the sprocket only turns a few revolutions and goes back again.

  • dsblox Feb 28, 2009

    I have the identical problem in the other direction (goes down 8 inches, up 8 inches and then stops). I just replaced the gears and reassembled the unit--so I must have put something back together improperly??? But it all looks right. What I've tried:
    * Light is not flashing so I don't think it is the safety sensors
    * I'm not even close to the limit contacts in either direction
    * Identical behavior no matter how I adjust up/down force in any combination.

    Any help would be appreciated.


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I figured out that when I replaced the gears, I damaged the RPM sensor. It was easy to swap out the old for the new and now it works fine.

Posted on Feb 28, 2009

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Don't know if this is everyone's problem, but it turned out to be mine. When I reassembled the opener after replacing the gears I had not properly re-attached the electrical connection to the limit switches. So it turned out to be "user error." After properly seating the electrical connector the opener operated properly.

Apparently, if the limit switches are not connected the garage door does what we've seen: move about 8 inches down, then 8 inches up, then flash the LED in groups of 5 blinks.

Posted on Feb 28, 2009

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What does the purple button light flashing on 1/2 horsepower craftsman garage door opener


I think the adjustment mode is on.

For example, that's from Craftsman manual:

""
Setting the Force
The force setting button is located on the left panel of the motor unit. The force setting measures the amount of force required to open and close the door.
1. Locate the purple button on the left panel of the motor unit (Figure 1).
2. Push the purple button twice to enter the opener into Force Adjustment Mode (Figure 2). The LED (Indicator Light) will flash quickly.
3. Push the remote control or control console (Figure 3). The door will travel to the DOWN (close) position.

""

Actually, you should just read carefully your garage door opener unit's manual.

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