Icom designed the fan circuit in such a way, the fan switches on at approx 28 degrees C. I dived in the circuitry, and found a way to lift this temperature to approx 35 degrees C. The mod if fairly simple, by just replacing a resistor, however the difficulty rate goes sky high if you see how large the resistors are these days. We are talking about R510 on the main unit. The resistor is located under the speaker, and can be accessed by lifting the top cover, and removing the speaker. At the top of the diagonally placed IC25 you will find the resistor. It is attached to PIN 71 of IC25. I marked the resistor in RED on the picture below. You can do 2 things: Replace the resistor (originally 39 kOhm) with a resistor of 22 kOhm. solder a resistor in parallel with the original one. in that case, you don't have to remove the very small original resistor, and thus can make things easier. You will need a resistor of 56 kOhm to use this method. If you successfully modified the IC-2820, you will never hear the fan again in normal circumstances. My fan is silent for over 6 months, and my rig works just fine. DISCLAIMER: Your mileage may vary, i am NOT responsible for ANY damage or faults. Modify your rig at your OWN RISK.