When my A/C turns off after a few minutes it makes a screeching sound that lasts about 20 seconds. You can hear it about two houses down it is so loud. My unit has a heat pump, and is about 5 years old.
I have had four HVAC people look at it and no one can figure it out. Two of them said they had never heard anything like it. I had the reversing valve changed about two weeks ago and the noise stopped for two weeks and now it is back.
Other than the noise, the A/C works great. What could be causing the noise?