I have replaced the worm gear assemble twice in my craftsman 1/2 hp garage door. what am i doing wrong. why does it keep turning to dust

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.

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.

Binding on the track?

Here are some things to check.

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.

The thing to do is remove the cover and watch the limit switch assembly. You should be able to see how it is supposed to work and determine what is wrong. A small gear on the end of the shaft turns the limit switch assembly to make contact and turn off the motor in each direction. Something may be broken or out of place. There is also a possibility your logic board is bad especially if you have had electrical storms recently.

you need to replace gear when the door is fully closed. then do your tweaking.

as long as the door is less than ten years old, sears will stock the part you need. you can contact them through this link.

http://www.searspartsdirect.com/partsdirect/index.action?psid=58709328&sid=PSx20071217x00001a

Unplug the unit and remove the cover, usually eight screws, if you see a lot of white dust in the cover check the nylon drive/worm gear, they will need to be replaced.

It sounds like you did a really good job! My Craftsman 1/2 hp gar. dr. opener has a red reset button on it on the l/h side as you are looking at the light/motor from the garage door opening. You have to take the light cover off to be able to see it. My reset button is on the same side as the ground wire. You might check the ground wire while you're there. I really hope that this fixes it for you (and me). I'm quite sure it will as you know your way around the garage door opener already. Good Luck and Let me Know (Please) if it fixed it or not. If I think of anything else, I'll let you know. Have a Good Day!

readjust the sensor controls on the side of the unit