The LiftMaster 841LM Automatic Garage Door Lock is an OEM security accessory that automatically deadbolts a sectional garage door when a compatible LiftMaster opener completes the close cycle. Integrated with myQ and Security+ 2.0 control logic, it verifies a locked status with the operator, prevents motor movement until it disengages, and then releases automatically before any open command—helping resist forced entry and back‑driving of the door. An audible click confirms engagement, and because the 841LM is managed by the opener, there are no separate remotes to program and no batteries to maintain.
The 841LM is a wired, low‑voltage accessory that connects directly to the motor unit and is intended for use only with select LiftMaster Automatic Lock–capable openers, such as the 8500W wall‑mount and certain newer myQ‑enabled DC drive models identified as “Automatic Lock capable” in their documentation. It is designed for residential sectional doors and works in conjunction with properly installed photoelectric safety sensors; it is not intended for one‑piece tilt‑up doors or operators that do not support the lock feature. Installation involves mounting the lock to the vertical door track, routing the cable to the opener, and enabling the Automatic Lock function via the opener’s control menu. As a replacement part or security upgrade for compatible LiftMaster smart garage systems, the 841LM adds monitored door‑lock status and automatic deadbolting without introducing additional radio components. For wider or specialty applications, consult LiftMaster guidance on the number of locks required and verify compatibility by model number before installation.