Review on Enhanced Cooling Fan for High-Speed Routers: Ultra Silent USB 5V Radiator with Speed Regulation Control - Compatible with RT-AC68U, AC86U, AC1900P, EX6200, and AC15 Models by Jeffrey Crutcher

My RT-AC86U gets very hot at 44c (2.4GHz), 51c (5GHz) and 71c (CPU). This seems to be the average operating temperature for this router. I have another identical router that is currently under warranty and running at the same temperature. The room where the router is located is around 65F year-round. Installing the coolers took less than a minute. I was very surprised that they run almost completely silent and don't seem to push through as much air. However, as the attached diagram shows, there is enough airflow to lower the temperature across the board. Resting temperature 34-44-49 degrees. The fans are attached to the back of the router using the included 3M double-sided tape that fits around the fan hub and does not block airflow. Fans are thin, light, brushless DC fans with pre-installed filters. At the moment I can only warmly recommend this cooler.