2017 iMac noise and erratic behavior
After my iMac is on for a few hours, it will start making a weird noise that is coming from the speakers and the volume of which is dependent on the output volume. The noise is like a cartoon sound of bubbles being produced rapidly. When this noise starts, the Apple menu behaves erratically - pointing the cursor at anything in the list results in the cursor jumping around and flashing. Also, the computer can’t be put to sleep. If I select Sleep, it just wakes up. Inevitably, when this noise starts, I have to shut down the computer - usually for an hour or so. I assume something is overheating but not sure what. Any ideas are welcome!
iMac (2017 – 2020)