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I'm curious on what you find out..

I'd still like to check it out some more, but I'm leaning toward the idea that it's worn sleve bearings in the motor. I've noticed such squealing happen in other things in the past, especially in fans. The fan in an old dehumidifier I was using had that problem intermittently, but eventually it became too bad, and would happen all the time. The weight of the fan blade, being metal might have tended to dampen the shaft at first, until the play in the shaft became too great. We had an old window fan with a metal blade that seemed to go through the problem similarly.

The resistance to wear of shafts and bearings in more modern motors are better, I think.

Consider that the pitch of the noise is likely related to the speed of the culprit.
Since the motor runs faster than the drive mechanism it's squeal is likely to be a higher pitch!
All senses are needed for troubleshooting!

That's a good thought!

You can pull the emergency release handle (for opening door when power is off). Running the motor back and forth without the door might help in your diagnosis ..

That's a good idea. I tried that and determined that the noise level of just the motor unit running was okay. That led me to the thought that the squealing noise comes from long threaded rod squealing against the long sleeve it's in. I'm thinking of applying a new coating of grease to the threaded rod.

Or..maybe the generic door rollers would benefit from a drop or two of mother earth's elixer

Lenp wrote: ↑Wed May 13, 2020 6:17 am Or..maybe the generic door rollers would benefit from a drop or two of mother earth's elixer

Dinosaur's Dynamic De-frictioning Drops?

The good ole 3-in-one.

dacflyer wrote: ↑Mon Apr 20, 2020 6:36 am I'm curious on what you find out..

So far the application of grease to the long threaded rod seems to have solved the problem. decided to go with synthetic grease supplied by the first well-known supplier of synthetic oil for the consumer market way back when.

I went away for a few months and there was plenty of new posts today I'm actually busier during the shutdown trying to work at home and be interrupted by kids frequently. Today I am finally back in the office, so peaceful