Radek

https://github.com/bigtreetech/BIGTREETECH-SKR-mini-E3/issues/623

Connect an electrolithic capacitor 1uF to the ventilator

On what date do you have Marlin compiled? Recently there was a problem with soft.PWM and fan control on STM32 platforms https://github.com/MarlinFirmware/Marlin/issues/20638 https://github.com/MarlinFirmware/Marlin/issues/22972 fixed: https://github.com/MarlinFirmware/Marlin/pull/23125

That will be the problem. The BTT version is 19 days old. The fix was uploaded 8 days ago. Compile your own current FW.

So that's bad luck

https://github.com/MarlinFirmware/Marlin/issues/23189

Try the new versions. Is 4 days old and may have a repair ... https://github.com/bigtreetech/Marlin/tree/SKR-mini-E3-V3.0-G0B1/Marlin If the fan does not work with the new version, try disabling the speaker

If necessary, reconnect the cables to the display. Find inspiration here: https://github.com/bigtreetech/BIGTREETECH-SKR-E3-Turbo/issues/40

Can you send your configuration files?

You have to allow #define USE_CONTROLLER_FAN and define the pin #define CONTROLLER_FAN_PIN PB15