The built-in fan of the ICOM IC-7300 is quiet noisy and turns on on every transmission. It does not seem to be temperature controlled. Follwing some information by DL2YMR I changed the fan to a Noctua NF-A8 as he showed in his video . I did not like to cut of the wires of the old an new fan especially because I had fitting connectors sitting in the spare parts box.
I just cut off the 3 3-pin connector from the wire of the new fan. The PWM wire (yellow) was just bent back into the shrink tube to isolate. The red and black wire was mounted to the crimp contacts of the JST PH2P connector. This way the new fan can be connected properly to the PCB.
Please be aware that this may eventually break your rig. Use at your own risk. I am not liable in any way for damage to your equipment.