Problem with craftsman garage door opener

Check the sensitivity on the back of the powerhead. If it's too light the door will touch the ground and come right back up if it's too hard you could damage the door b/c it's going down with too much force. This is the amount of force that you want the door to hit before returning back to the up position if something is in the way, some people use a roll of paper towels to check this force. Hope this helps.

There will be adjustment knobs on the side of the unit. Usually two white knobs that you have to turn with a small flathead screwdriver. These are the limit / load adjustments.

These adjustments are VERY sensitive, so be patient!