Chasing a phantom slow door in an old Otis in downtown Cleveland

Had a car in a 1980s office tower that would take exactly 47 seconds between landing and opening the doors, and after swapping relays, checking the door operator, and even replacing the limit switches on a Tuesday, I finally found the issue was a worn out clutch spring on the motor that only showed up when the car was hot, took me about 9 hours across two days - has anyone else had a gremlin like that where you overthink the logic and it ends up being pure mechanical?

2 comments

2 Comments

zarar671mo ago

Drove me nuts for years thinking every slow door was a logic or controller issue until I had a similar one in an old Montgomery in a hospital. After chasing limit switches and door timers for hours, turned out the door arm was slightly bent and would bind only when the car was fully loaded. I was convinced it was electrical because the symptoms were so random. Now I always check the mechanical linkage first before touching any wiring, your mileage may vary but that clutch spring story made me rethink my whole troubleshooting flow.

emmaj331mo ago

Was that bent door arm visible at all when you looked at it, or was it so subtle you couldn't spot it without taking the whole assembly apart? Id say that kind of intermittent binding would drive me crazy because everything looks fine when you're staring right at it. Trying to figure out how much force it took to make that arm flex must have been a real headache.