I did the same as you, disconnected all slave wires hooked red and red black and black to master, gates open and close but I cannot get the slave to stop same as master. I've screwed the arm in and out to try and set the stop the same. It just wants to go to far open
Fm502. 4 beeps. Slave gate moves 2 inches. Swapped out rev counter. Batteries at 13.5. Still not working. I like the idea of disconnecting the slave wires then hooking red and black only to master. Does this work any ideas.