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
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.
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.
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.
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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