I’ve wired the LFM-20 into the liftmaster garage. I’ve connected it to my SmartThings hub V2 and changed it to virtual momentary contact switch. The Liftmaster opener is giving me an error code of arrow up once, arrow down 3 times. The two blue wires are constantly hot and turn off momentarily when hitting the button on the phone to operate the switch. I do hear the switch operate when operating the button on the app. Does anyone have any recommendations??
Below is liftmaster’s explanation of the error code. My wall buttons are still working normally.
Up Arrow Flash: 1
Down Arrow Flash: 3
Symptom: The door control will not function.
Solution: The wires for the door control are shorted or the door control is faulty. Inspect door control wires at all staple points and connection points and replace wire or correct as needed.
sounds like this Liftmaster is not compatible with a single momentary switch (buttonpress). Your existing wall-mounted controller to the Liftmaster is probably not a simple switch. Hard to know for certain without seeing a part# for the controller or the Liftmaster garage door opener.
There is a similar problem in this thread below, with possible fix.
I wired a garage door remote to the wires on the Linear opener and got this to work. I am happy to provide support if you need it, so please let me know. I used a multimeter after disassembling my remote to determine which part of the circuit closed the switch and then I soldered the wires of the garage door controller to the remote. I admit it was nerve racking and I thought I was going to ruin the remote.
If you have a multimeter, put it in continuity mode and test multiple areas near the button to determine the sides that need to be connected to represent a closed switch. From there it is an exercise in steady hands and soldering.