Only have 1 of these units on my route. Been running trouble free for about a year now. 3 days ago unit was out of service with a DTO fault only. Door open protection fault. Thought it was not seeing the open limit.went over doors mechanically and cleaned all car and hall door sills. Everything seems good. Cleared ram of the fault. Ran car for an hour with no issues. Next morning same fault. Cleared fault and car ran all day no issues. Next morning same fault. No one uses elevator at night in this building other than the cleaner. Is there something I’m missing here? Is there a certain way to reset a fault on an Otis 211?

Assuming its an I Motion I would start by relearning the door. If you still have issues I would test or replace the limits, sensors, and relays on the board. I believe the operators use a binary count for slowdowns and such, maybe the belt is slipping and something is being thrown off?

Maybe when not in use, the door fully closed or open switch or relay is gaining resistance? Did you check all limits?

The door motor on the AT400 (linear type) operator can fail intermittently in one direction only. Usually you can tell by manually pushing the door open or close and it feels like there are screws in the car sill groove, but piloting the doors with power, it seems ok...until it gets real bad.

Thanks guys for your input. I forgot to mention that I did do a relearn on the last visit so fingers crossed that the issue will go away. if not then I will start changing out limits and such. I will chime in once this issue is resolved

Seems like doing a relearn on the door operator has this issue solved. Why all of a sudden the door was faulting out fully open is just one of those strange and wonderful things that we come across now and then!