why does my airport extreme base station over heat?

Please do an experiment for me.

Open the airport utility.. click on your AE icon and click edit.. go to the top menu and grab the diagnostics.. it is named differently in High Sierra.. but is still there.

Open the latest ThermalInfo (it will be on the bottom with today's date.)

The key values are fan duty cycle rate and RPM.. as well as the Tmps Internal (0-4) although the numbers are not in human readable form..

Turn off the fan in the laptop cooler and wait a few hours for the Temp to stabilize.. Then take another snapshot of the ThermalInfo .. you might need to wait a while (a day) for a more current one to be generated.. or just do a quick power cycle of the airport so you get the latest numbers.

Ran out of edit time.

If you check a thread like one just below yours.

why is my airport extreme overheating?

Turning off file sharing has worked for some people.

It could be worth a go.. unless you actually use file sharing then it is useless.

I am going to guess you have a Gen6 AC tower model Airport Extreme.. the problem is fairly common.. tell me if the guess is wrong.

How old is it? The Gen6 was introduced mid 2013 so if it is early model it is coming up to 5 years.. that is the standard operating life of domestic grade routers.. better than most actually.

Fan issues.. very common.

Fan needs cleaning which is not a minor job. If the AE is new or still within Applecare on a computer, ipad or appleTV get Apple to replace it.

Otherwise you need to look up instructions .. tell us if you want more but there are several posts as well as ifixit instructions.

Sensor failures.. not as common but do happen.

One of the Temperature sensors is giving false reading.. this is total pain because it is really hard to fix.. there is a sensor on the power supply so if you fix the fan it might be worth looking into power supply failure as well.

My AirPort Extreme is placed on a Laptop Cooler.

Mt AirPort Extreme is kept "cooled down" to the Laptop Cooler's utmost efficiency.