Let it sit on the screen and watch it.
Let the machine go idle.
When the fan runs fast what does task mgr show?
CPU fan suddenly runs fast for about 30seconds every 10 minutes or so. This only happens when pc sits idle, does not happen when being used.
Home built i5 with Gigabyte m/b, Windows 10, 2 years old, cleaned heatsink weeks ago. Downloaded Core Temp, CPU temp - runs typically 28-33C. Can't figure why. Thanks