LiftMaster 3840 Support Questions

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Where Can I Find Complete Technical Info For A Liftmaster 3840 Garage Door Opene
Need to know Logic Board jumper settings and communications protocol for remote devices.

Door Will Not Close!
When I press the button to close door, it goes down a couple inches and then reverses and goes back ...

Will A 485 Lm Battery For A Model 3850 Work On A Model 3840?
I need a new battery for my garage opener, model 3840. All of the batteries I have seen are 485LM fo...

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