Craftsman 1/2 hp garage door opener problem I've replaced th...

Craftsman 1/2 hp garage door opener problem
I've replaced the sproket assembly in my 1/2 hp Craftsman chain drive opener and now the unit will only runfor about two seconds one directionand then two seconds the other direction. Anyone have any tips for me?

Did you ever get this problem fixed? I just replaced the same worm gear and sprocket and my Chamberlain does the same thing. It goes up about 1 foot then back down.

I am having the same problem. Did you figure out what's going on?

When you remove the chain from the sprocket, you have to maintain the relationships amongst several items. Namely, the relative position between the trolley that works the door, and the up/down contactors.

When you take the slack out of the chain in order to remove it from the sprocket, I try to just hang it on the end of the rail, rotating as little as possible.

After I replace the drive shaft/gear assembly (the easy part) I determine whether the unit is sitting on the up contact or the down contact. The holes in the side of the case tell you which screw is up and which is down. If it happens to be in mid cycle just leave the small helical gear off of the bottom of the shaft and spin the worm gear until one of the contacts is being made.

Then re-install the chain so the trolley is in relation to the appropriate contact and only minor adjustments should be necessary.