Shoutout to the old Otis that finally gave out on me

I work on a bunch of older elevators in a hospital downtown, and Tuesday one of the Otis units from the 80s just stopped leveling. The door operator was dragging and the hall calls would drop after a second. I spent 3 hours tracing a bad connection in the controller cabinet behind a panel nobody had opened in years. Ended up finding a loose terminal block that was barely hanging on. Has anyone else had to deal with these old solid-state relay boards acting up?

3 comments

3 Comments

mila_flores819d ago

Oh man, "controller cabinet behind a panel nobody had opened in years" is the story of my life. I deal with an old Otis in a 12-story building and last month I had the exact same loose terminal block problem on one of their M-BSS relay boards. That thing was so heat cycled the plastic around the screw terminal was cracked and barely holding the wire. Ended up cutting back the wire and using a new ring terminal with a star washer to bite into what was left of the terminal. For the door operator drag, check the hall limit switches too, those microswitches get sticky when the grease turns to tar. Also worth spraying the relay contacts with Deoxit before you start chasing ghosts. Sometimes those old solid state boards just need a good cleaning and reseating.

avery_lopez2d ago

That ring terminal with a star washer trick is solid. I've done the same thing on a couple of old Otis boards where the terminal plastic was just crumbling. If the board is still acting flaky three months out, I'd check the solder joints on the relay pins themselves. Those M-BSS boards have a bad habit of cold solder cracks from the heat cycling. Also try reseating all the ribbon cables to the main processor board, I chased a phantom fault for two days once just to find a loose cable.

jesse99419d ago

The M-BSS board is exactly what I was dealing with... that heat cycled plastic around the screw terminal is a nightmare. I had one where the terminal block actually broke off the board when I touched it. Did you end up having to replace the whole relay board on yours, or was the ring terminal fix enough? Because I'm three months out from that job and I'm already seeing the same board acting flaky on another floor.