Chamberlain 8500 Manual page 32

Troubleshooting
Troubleshooting (Continued)
My door will not close:
The safety reversing sensor must be connected and aligned correctly before the garage door opener will move in the down direction.
• Verify the safety sensors are properly installed, aligned and free of any obstructions.
The garage door opener strains to operate door:
• The door may be out of balance, or the springs may be broken. Close the door and use the emergency release handle to disconnect
the door. Open and close the door manually. A properly balanced door will stay in any point of travel while being supported entirely
by its springs. If it does not, disconnect the garage door opener and call a trained door systems technician.
The garage door opener motor hums briefly, then won't work:
• The garage door springs may be broken. See above.
• If the problem occurs on the first operation of the garage door opener, door may be locked. Disable the power door lock.
The garage door opener won't operate due to power failure:
• Manually open the power door lock.
• Use the emergency release handle to disconnect the door. The door can be opened and closed manually. When power is restored,
pull manual release a second time.
• If a Battery Backup is connected, the opener should be able to operate for up to 24 hours without power.
Door loses limits.
• Collar not tightened securely. Tighten collar (see Assembly Steps 1 and 2) and reprogram limits (see Adjustment Step 1).
The garage door opener moves when the door is in operation:
• Some minor movement is normal for this product. If it is excessive the collar will wear prematurely.
• Check to make sure the torsion bar is not moving left/right excessively.
• Check to make sure the torsion bar is not visibly moving up and down as it rotates.
• Check that the opener is mounted at a right angle to the jackshaft. If not, move the position of the mounting bracket.
Power lock makes noise when operating.
• Call LiftMaster dealer for replacement power lock.
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