About a month ago my son-in-law replaced a worm drive gear and a large round gear in my Chamberlain 1/2 hp garage door opener. Installation of parts seemed easy enough but when he was finished the door would only open a foot or so. He reread all the instructions and decided the limit switches needed to be reset. The door opens about 3 foot now and will not come back down. He got frustrated and now has left it up to me to fix or get it fixed! He had the switch completely apart and now I am not sure where the original settings were! Any help would be appreciated as we all know winter is coming and I don't want to be in the cold!