Good chance it’s the condenser fan motor - the bearings/bushings can go bad - often the noise is a high squealing pitch, at least it was when mine went bad.

Try this - pull the disconnect to the condenser, when with a screw driver, stick, branch, … try to spin the fan blade through the grill - if it only turns a 1/4 to 1/2 a complete revolution, as opposed to several complete revolutions, with a good, hard spin, then it’s likely bad bushings in the fan motor.

I ordered a OEM motor and replaced mine myself - I guess I saved a few hundred as a DYI. It was an easy job, but if you do this watch several Y/T videos of HVAC techs doing it first - the most common issue is removing the fan blade from the motor shaft, as they are often rusted on and there are several tricks the techs use to help remove them - fortunately I did not not encounter that problem. Secondly, the fan must the placed in the exact location on the new motor as the old motor - so you need to mark the location on the old motor shaft before removing the fan, and place it in the exact same location on the new motor shaft.

HVAC techs often carry a universal condenser fan motor on their trucks, which are fine, but they usually have an extra wire and the fan motor wire colors don’t match up with the original - that can be a bit confusing for a newbie to make all the right wiring connections, but one should not have that issue if you use an OEM replacement motor.

ETA: when the bushings heat up and expand you get the squealing noise, not at first, as you describe - same with mine.

This post was edited on 4/26/23 at 11:29 pm