Garage Door Opener Problem

One of my 3 Sears Crafsman 1/2 hp garage door openers is not working. It is stuck in the open position, so I closed it by releasing the emergency handle.
The trolley is firmly wedged against the cover protection bolt instead of having stopped at a normal 2 - 4 inches short of the bolt. The small length of chain on one side of the motor just before the cable feels extremely tight and won't budge, while there is a little play in the chain on the other side of the motor (the long length of chain). Also the indicator light next to the button for changing the remote code is blinking.
When I press the button in the garage to close the door, the motor hums for a couple of seconds, then stops humming, but the trolley won't move.
The manual isn't clear, and I'm guessing the issue is straightforward, I'm just don't know what the issue is.
Please advise.
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contact sears??

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Dimitrios Paskoudniakis wrote:

This is a common problem with Chamberlain/Liftmaster/Sears openers, and it happened with my early 1990s Sears. I ended up removing the chain and cycling the opener a few times without it to resynchronize everything, but it's possible your opener has a problem with the limit switch mechanism, which tells the opener when the door is either fully opened or fully closed. It's about $20 from Chamberlain, but it's probable yours isn't damaged but merely overran one of its limit switches. If Sears won't help you (or wants to charge you for phone help), try phoning Chamberlain since they're worried about product liability caused by a big door slamming down on a person.
If you work on the opener while it's powered, have a helper standby to pull the power in case the opener grabs your hand or hair, and stand on wood to keep yourself electrically insulated. Don't manipulate the limit switches with a screwdriver but instead use a plastic or wooden rod. A chopstick, especially a bamboo one, is good for this.
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on 10/6/2007 6:44 PM Dimitrios Paskoudniakis said the following:

Unplug the door opener. Remove the case from the opener. Look inside at the gears. You will find that they are nylon and are probably worn badly. If so, check for the model number of your opener (My model number is behind the bulb lens and is 139.53603, so it is a Chamberlain). Find a Sears parts store in your area or go to Sears.com ( http://www3.sears.com/ ), and check for the repair kit for your model. It contains new gears, bushings, washers, lubricant, a couple of hex head screws, and other small parts. I paid around $23 for the kit 2 years ago at my local Sears parts store and used only the gears. I don't know if your model number is the same as mine, but if it is the same, here are all the numbers from my kit parts box: A couple of large numbers; 65409 and 41A2817. Also smaller numbers MFG code 125512, and the SKU under the bar code D98M65409.
--

Bill
In Hamptonburgh, NY
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I fixed it by loosening the chain length adjustment bolts until there was some slack in the chain. The trolley could then moved to the closed door position when pressing the button on the wall. I then turned the up setting screw a couple of turns toward "less up", so that the trolley doesn't approach the guard bolt. Then I returned the chain length adjustment bolts to their original position. Solved.
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