The Asus RT-AC86U wireless router has a stand-up design and its heat management is relying on passive cooling.
Unlike those flatbed routers which we can easily provide heat dissipating solution to them by using normal laptop USB cooling fans, the temperature management solution for this stand-up router needs some tweaking to attach external fans to it. Luckily, there is ready made solution in the market, and it is quite cheap too.
If you are using AsusWRT-Merlin firmware in the router, you are able to read the runtime temperature reported at its Broadcom BCM4709 processor (CPU), Broadcom BCM4365E 2.4GHz WiFi SoC chipset and Broadcom BCM4366E 5GHz WiFi SoC chipset respectively.
In normal operation, the temperature at 2.4GHz WiFi chipset stays around 50-55 degree Celsius and the temperature at 5GHz WiFi chipset stays around 55-60 degree Celsius. However, the dual-core CPU temperature is always on the high side, staying above 70 degree Celsius, and there are users reporting that it can go up to above 90 degree Celsius.
If you are feeling uncomfortable with these kind of temperature readings and would like to lower them down to a more comfortable level, you just need to install a pair of external USB cooling fans at the back of the router.
The two 7cm fans are powered by 5V DC from the USB 2.0 port of the router itself. You can also plug it to the router's USB 3.0 port, but that port is normally used by external storage, USB Internet dongle, etc.
It is attached to the back of the router using 3M double-sided tape provided in the cooling fans set package.
Within 20 minutes, the pair of fans are able to cool down about 5 degree Celsius to both the 2.4GHz and 5GHz chipsets respectively. They can effectively cool down the temperature of the CPU by a whopping 20 degree Celsius.
With this heat dissipating solution, now the temperature at the 2.4GHz chipset reduced to around 45 degree Celsius, and the temperature at the 5GHz chipset reduced to around 52 degree Celsius. The CPU temperature greatly reduced to around 53 degree Celsius.
If I power down the fans by unplugging it from the router's USB port, all the 3 temperature readings will gradually increase, and went back to the previous high level within 20 minutes.
The fans are rotating at relatively low speed at 2100 RPM, making them pretty quiet. You can hardly hear their noise unless putting your ear very close to them during silent night.
According to their specifications, their noise level is at 18 dBA only. Their lifespan is around 50,000 hours, which is equivalent to over 2000 days, long enough to serve for the entire lifespan of the router.
Other than Asus RT-AC86U, this pair of USB cooling fans can also be used for Asus RT-AC68U router as both of them are having very identical size and casing build.