my opener's light won't turn off automatically anymore, it just stays on for hours

Diagnosis

The LiftMaster 8355W utilizes a logic board that manages a specific "Light Timeout" window. When the lights stay on indefinitely, it is typically caused by a logic glitch where the timer fails to trigger the "off" command, or the "Light" button on the wall console has been accidentally toggled into a "Permanent On" mode. This often happens after a power surge or a momentary voltage drop that confuses the board's volatile memory. To confirm if this is a software glitch or a hardware failure, trigger the door to open and close. If the light remains on regardless of the door's position and does not respond to the wall console button, the issue is likely a stuck relay on the logic board. However, if the light responds to the manual button but refuses to time out, the timer settings have been corrupted or overridden.

How to Fix It

To resolve the light timeout issue and restore the default automatic shut-off period, follow these precise steps to reset the logic board's lighting parameters:

1. Locate your wall control panel (the wired button inside your garage).
2. Press and hold the "Light" button firmly for exactly 10 to 15 seconds. Do not let go until you hear a single audible beep emanating from the motor unit hanging from the ceiling.
3. Release the button immediately after the beep. This action clears the "Permanent On" override and restores the factory default timeout, which is typically 4.5 minutes.
4. To verify the fix, press the light button once to turn the lights on, then wait. The lights should now extinguish automatically after the designated window.
5. If you have a wireless keypad, ensure no buttons are stuck in the "down" position, as a jammed button can send a continuous signal that keeps the logic board in an active state, preventing the timer from starting.

If That Didn't Work

• Perform a Hard Power Cycle: Unplug the 8355W motor unit from the 120V AC outlet. While the unit is unplugged, press and hold the manual release cord to ensure the carriage is free, then wait at least 30 minutes. This allows the capacitors on the logic board to fully discharge, clearing any "ghost" commands in the RAM that a simple button reset cannot fix.
• Inspect for "Force" Errors: Check if the opener is attempting to close but is being stopped by an obstruction (even a small pebble). If the door doesn't reach the fully closed limit switch, the logic board may believe the "cycle" is still in progress, which keeps the lights on for safety. Clear the tracks and ensure the door closes completely.
• Replace the Light Bulbs: If you are using high-wattage incandescent bulbs, the heat buildup in the housing can occasionally warp the plastic sockets or cause a short in the bulb's base, tricking the board into a constant-on state. Switch to 60W equivalent LED bulbs to reduce heat and draw.
• Logic Board Replacement: If the light stays on even after a hard reset and the bulbs are replaced, the light relay (a small mechanical switch on the circuit board) has likely welded shut. This is a hardware failure. You will need to replace the entire logic board assembly, as the relay is soldered to the board and cannot be replaced individually.

Heads Up

• Avoid using bulbs that exceed the maximum wattage rating listed on the motor housing; overheating is the primary cause of premature logic board failure in the 8355W series.
• If you experience frequent "glitches" with the light timer, install a small surge protector on the power outlet to prevent voltage spikes from corrupting the board's memory.
• Ensure the wall console wires are securely tightened in the terminals; a loose "white" or "white/black" wire can cause intermittent signals that trigger the lights to stay on.
• Regularly clean the photo-eye sensors; if the sensors are blocked, the door won't close, and the lights will stay on indefinitely as a warning signal.