Getting out of the car at the end of a long day to open the garage door can be frustrating -- especially when the automatic garage door opener sounds like it's working, but isn't. There are a number of reasons why the motor will run, but the chain doesn't move.
Carriage Disengaged
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Most garage doors have an emergency release -- typically a red pull cord -- that allows the door to be opened and closed manually. When the cord is pulled, the motor is disengaged from the chain. The motor will run, but will not move the chain. If the cord has accidentally or purposely been pulled, the automatic door opener will not work until the chain is re-engaged. This process varies by manufacturer and model, but many openers can be re-engaged by pulling the emergency cord a second time.
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Chain Too Tight
If the chain was installed too tightly on the garage door opener, it can make opening the door more difficult for the automatic opener. This excess tension causes the gear that moves the chain to grind down. If the gear becomes too worn, it will no longer be able to move the chain. In this case, the motor will run and the gear will turn, but the chain will not move and the door will not open.
Inappropriate Size
The size and power of the garage door opener must be properly matched with the weight and size of the door. If the door is too heavy for the opener, the mechanisms that lift the door can wear out quickly. Just as with a chain that is too tight, the teeth or cogs on the gear that move the chain will wear down and it will no longer be able to move the chain to open the door.
Gear
If the gear that turns the chain becomes worn, it will need to be replaced. This can be done by a repairman or an ambitious homeowner. The motor housing must be opened and the chain disengaged before it is replaced. Removing and replacing the old gear is not difficult. Lining up the screws in the small space to reattach the assembly and motor housing is the challenging part of the task.