2018 MacMini fan not running as often as it used to ?

Open the MacFanControl panel with the temp. read outs.

Look for the highest temp. read out. On my 2018 it is generally the CPU Diode.

Them go to the Sensor Base Control and select that temp sensor.

Now set the low setting for that sensor to about 150 and the max temp. setting to about 190 and click OK.

That should run the fan at default until the temp. goes above 150, then as the temp. increases over 150, the fan should slowly ramp up to help maintain a decent temp.

Sorry I’m away on my iPhone and unable to post any screen shots of my Mac FanControl setup for about another hour or so.

Sorry I'm using the CPU PECI on my 2018 Mac Mini, not CPU Diode. The CPU Diode is used on one or two of my earlier Mac's.

For the most part the fan runs at the default 1700rpm until I start an intense CPU process and then the temp. never goes much over 165/170 with the fan running at around 2800/3000rpm. Then as soon as the process finishes the fan shortly returns to the default speed.

FWIW I have been doing this with all of my iMac's and Mac Mini's for around 15 years now, and have never had any of them prematurely fail from over heating.