If you can hear your garage door motor running for what seems like the full amount of time it normally would take to open or close the door, but the door doesn’t move, chances are the disconnect switch has been enabled. Every garage door opener comes with a disconnect switch in case you lose power. This allows you to open or close the door manually so your car isn’t stuck in the garage until the power comes back on. http://www.youtube.com/v/Z_eZc-kh40c&feature=youtube_gdata
• Extension springs: Garage door extension springs stretch to provide lifting power for the door. These springs are typically made of steel and mounted above the horizontal track of the garage door. A safety cable should run through your extension springs to prevent possible injuries or property damage. Extension springs are the most common type of garage door spring for residential use and can break after excessive usage.