Cooling tower fan not getting detected

General
1

Hi,

I’m facing an issue with the CPU tower cooler fan on my Pironman 5 setup.

Setup

  • Raspberry Pi 5

  • Pironman 5 case (using the provided 4-pin PWM CPU fan)

  • Raspberry Pi OS (tested on both NVMe and microSD)

Issue

  • The CPU fan spins briefly at boot

  • After the system fully boots, the fan stops and never spins again, even under load

  • CPU temperature crosses 50°C+, but the fan still does not start

What I’ve tested

  • Reinstalled Raspberry Pi OS (both SD and NVMe)

  • Tested without Pironman software installed

  • Reseated the fan connector multiple times

  • Confirmed the fan is connected to the Pi 5 4-pin fan header

Diagnostic output

ls /sys/class/thermal/

Output:

thermal_zone0

:backhand_index_pointing_right: There is no cooling_device0, which suggests the fan is not being detected by the system.

I also tried:

cat /sys/class/thermal/cooling_device0/cur_state

Result:

No such file or directory

Observation

  • Fan gets power at boot (spins briefly)

  • But appears not detected as a PWM fan by the OS

Question

  • Is this a known issue with the Pironman 5 CPU fan?

  • Could this be a cable / pinout / compatibility issue with the Pi 5 fan header?

  • Is there any additional driver or configuration required for the CPU fan (not the RGB fans)?

Any guidance would be appreciated.

2

The cooling tower is directly controlled by the Raspberry Pi’s fan control strategy. You can run the following commands to check whether the fan is working:

Keep the fan running at full speed
pinctrl FAN_PWM op dl

Stop the fan completely
pinctrl FAN_PWM op dh

Let the fan follow the Raspberry Pi’s default fan control strategy (typically starts at around 50°C)
pinctrl FAN_PWM a0

Please run these three commands to see if the fan responds properly. If it works as expected, you can simply leave it with pinctrl FAN_PWM a0.

By the way, may I ask — were these fan testing commands provided by an AI? Recently, I’ve noticed many people using incorrect commands when testing Raspberry Pi fans with the help of AI.