How to silence the fan on a CM5 after shutdown

Out of the box, if you buy a Raspberry Pi Compute Module 5, install it on the official CM5 IO Board, and install a fan on it (e.g. my current favorite, the EDAtec CM5 Active Cooler), you'll notice the fan ramps up to 100% speed after you shut down the Pi.

That's not fun, since at least for a couple of my CM5s, they are more often powered down than running, creating a slight cacophany!

I created the forum thread Compute Module 5 Fan goes to 100% on shutdown, and through some back and forth, it was found the firmware on the CM5 needed a little tweaking to support powering off the fan completely on shutdown.

In this December EEPROM update, Raspberry Pi added some code to ensure the fan would power off (and stay powered off) on shutdown, but only if you have:

POWER_OFF_ON_HALT=0

In your Pi's EEPROM config.

First, make sure your firmware is up to date, e.g.:

$ sudo rpi-eeprom-update 
BOOTLOADER: up to date
   CURRENT: Wed  5 Nov 17:37:18 UTC 2025 (1762364238)
    LATEST: Wed  5 Nov 17:37:18 UTC 2025 (1762364238)
   RELEASE: latest (/usr/lib/firmware/raspberrypi/bootloader-2712/latest)
            Use raspi-config to change the release.

Run sudo rpi-eeprom-update -a to update to the latest version, if needed, then reboot.

To edit the EEPROM config, run sudo rpi-eeprom-config --edit, and add the following line at the bottom:

POWER_OFF_ON_HALT=0

Save that change, wait for the config to apply, then reboot.

Now, next time you shut down the CM5, it should be blissfully silent.

Hackaday user Eontronics also designed a modchip that can be soldered onto the CM5 IO board for a hardware fix for this problem, if you can't use the POWER_OFF_ON_HALT=0 option.