Replaced sprocket and worm gear on chamberlain 1/2 opener
I replaced the sprocket & worm gear on my Liftmaster 1255 and it only raise 6 inches & reverses automatically and stays open 2 inches. Green light blinks 5 times...no limit or force adjustments make a difference? I'm stuck....
Re: replaced sprocket and worm gear on chamberlain 1/2...
The motor shaft may not be pushed in all the way. Check to see if the motor shaft is sticking out past the end of the motor more than about 1/2". If so, then remove the black cup on the other end of the motor shaft and then losten the two set screws holding on the collar. Then push the motor shaft all the way in toward the circuit board and then tighten the collar back on. The shaft has to be all the way forward to allow all the travel the gears need to take the trolley completely back and forth.
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If your drive gear is not meshing with the worm gear it is because it is worn out. You'll need to replace it post haste. The part number is 41A2817 and is available at Sears or any good door opener service company.
Loosen the chain enough
so that you can remove it from the sprocket above the motor unit.
With the door closed run the motor until the sprocket turns clockwise
and stops. With everything attached replace and tighten the chain.
Some adjusting of the up and down limits will probably be required.
Make sure you put the black cup back on
the end of the motor shaft and that it is pressed all the way on.
Make sure the RPM sensor is plugged in. If neither of these are the
issue, then you probably did not have the motor shaft pushed all the
way back when you tightened the coupler after replacing the worm
gear. Loosen that coupler up and from the front of the motor
(opposite end in which the coupler is on) push the shaft back as far
as it will go. Hold it there while you tighten the coupler back up
and then try it.
I have a 1265 and took the cover off (unplug first).
There are screws securing the cover: 2 on each side at top, 2 at either end bottom.
Then I disconnected the chain.
There are 3 hex head screws securing the drive gear assembly (of course they thread from the inside out which makes taking them out a bit time consuming). Take care not to damage the circuit board or other electronic connections.
Then at the bottom of the shaft is the "limit switch assembly" that is clipped into the metal housing. Squeeze the 2 on the outside and it should swing free.
Then at the very end of the shaft there is another plastic gear. It is secured by a 3 prong plastic clip. Pull the outside clips away from the shaft while pushing the center piece back through the shaft. The gear should come off and you can now remove the gear and sprocket assembly up through the assembly.
call 800 528 2817 and order the "Gear and Sprocket Assembly".
I am waiting for the part and assume we reverse the order above to reinstall.