We have two Lennox 13Acd outside units. One upstairs and a smaller one downstairs 13ACD-030-230-03. The smaller one at times makes a nasty noise at startup. I've recorded the noise
You can hear the upstairs one running during the first part of the video and then the downstairs unit kicks on with a nasty racket.
I've had the folks that installed the units take a look. They thought it was the fan motor and replaced the motor. This didn't make a difference. They are still convinced this is somehow the fan motor making the noise.
I've seen references to possible freon pooling where the noise occurs when all the freon has to be pumped back up. The noise occurs more frequently when it's hot outside. Both units have the inside unit up in the attic.
What is that awful noise?