Raspberry Pi PoE HAT Fan Noise

The latest Raspberry Pi PoE HAT on a Pi 4 is awesome! One cable to the right switch and you’ve got power and internet. One runs Homebridge giving Apple Home access to Ubiquity cameras, the Nest, and a few other custom things. It’s a great combination, the only thing I need to do is put Homebridge into docker and put the configure script into GitHub in case things fail. But there is one glaring issue with the PoE HAT. The fan. It’s loud! Very very very loud. It sounds like a basketball mosquito every 30 seconds. At 104°F (40°C) the fan turns on until the temperature is 102.2°F (39°C). It. does. this. all. day. and. night. long.

The solution is fortunately simple:

1. Shutdown your Pi.
2. Mount the SD card.
3. Open the file: /boot/config.txt

4. At the beginning of the file add the following:

# PoE HAT Fan Speeds
dtparam=poe_fan_temp0=55000
dtparam=poe_fan_temp1=60000
dtparam=poe_fan_temp2=65000
dtparam=poe_fan_temp3=70000

5. Plug the SD card back into your Pi and enjoy

My fan goes on at 55°C, increases again at 60°C, again at 65°C and full speed at 70°C. You can use the command to check the temperature and tweak the values above according to your environment.

vcgencmd measure_temp

I do think I need a good heat sink and chances are you do as well. But most heat sinks use a sticker which acts as a thermal insulator. You want thermal paste but then it’s difficult to hold it to the Pi, but this will be a discussion for a future post.