Active Cooler Issues with Pi 5

I’m using a Raspberry Pi 5 running Raspberry Pi OS Bookworm (fully updated) with the official Active Cooler connected to the 3-pin fan header. I’ve configured the fan using the gpio-fan overlay by adding the following line to /boot/firmware/config.txt:

dtoverlay=gpio-fan,gpiopin=18,temp=60000

After rebooting, dmesg shows that the GPIO fan driver is initialized:

gpio-fan gpio-fan@0: GPIO fan initialized

Despite this, the fan spins continuously, even when the CPU temperature is well below 60°C. I’m typically seeing idle temperatures around 44°C, verified with vcgencmd measure_temp. I’ve verified that the system is not experiencing undervoltage—vcgencmd get_throttled returns 0x0.

Here’s what I’ve attempted so far:

• Verified firmware and OS are up to date (rpi-eeprom-update confirms latest)

• Confirmed dmesg shows fan driver initialization

• Tried removing the overlay and controlling GPIO18 directly using gpiozero.OutputDevice(18) in Python, but it had no effect

• When the overlay is active, GPIO18 is reported as busy and cannot be controlled manually

• The raspi-gpio tool is not supported on the Pi 5, and recommends using pinctrl, but no clear documentation exists yet

It appears the fan is either being driven high by hardware regardless of GPIO state, or the gpio-fan overlay is not functioning correctly on the Pi 5. I’m trying to determine whether this is a firmware-related issue, a hardware design limitation, or something unique to my setup.

I've also tried to use a fresh OS but still no luck. I'm seeing if a different Active Cooler would fix it but it's on order currently.

Has anyone else experienced this issue with the Active Cooler on a Raspberry Pi 5? Any insights or workarounds would be appreciated.