This scripts are tested on RaspiaOS 64 bits upgraded to Debian Bullseye. You should use the next guide (based on the official website of the GeekWorm X735. This packages are upgrade to use Python3 (Python2 is deprecated):

sudo apt install python3 python3-smbus python3-pigpio
sudo apt install pigpio
sudo apt install git
git clone https://github.com/thorkseng/x735-v2.5/
cd x735-v2.5
sudo chmod +x *.sh
sudo bash install.sh
sudo reboot

The shell script "install_service.sh" will create a new service in the folder /etc/systemd/system/ with the name x735fan.service. Will enable and activate it and check that it is running. In that case will remove from .bashrch the execution of the .py file. The only need to do it it's execute the script:

bash install_service.sh

For activate the fan manually you can do with the next command, also, this command is added (in background) in the .bashrc of the profile of the user:

python3 pwm_fan_control.py

For read the speed of the system you need to use python3 instead python

python3 read_fan_speed.py 

Based on the GeekWorm user guide and the original repository of GeekWorm.com

Feel free to copy and modify :)