Post originale di: RickP ,
There is an 'open force' adjustment that can be changed. Sometimes it goes out of adjustment over time as the weight of the garage door can change with humidity or moisture and/or the springs change tension especially after being replaced. Or as machead3 states, through vibration from ther drive train. The manual for this opener can be downloaded: http://www.managemylife.com/mmh/pd_download/lis_pdf/OWNM/L0809294.pdf Reference page 13.