I cannot find my srvice book and am having trouble with my garage door opener. It is an over head door fast opening model. It will start up and stop about a foot off the floor. Sometimes it will work perfectly. This occurs with all controls; the remotes and the wall switch. If I hold the wall switch in all the time it will open. Can some one help. Thanks Paul

Check the sensors at ground level .They my have become unaligned.

Thanks for your reply. I checked the sesnors and they are both showing a steady light on them. If I block the path they start flasing so I don't believe that is the problem.. Thanks agaiun for answering. Paul