Does an external cooling fan void the warranty?

external fans do nothing, they actually hinder the cooling performance and provide zero benefit.

They absolutely can void the warranty

For example using the infamous intercooler on 360would void your warranty because it's a fire hazard. It would often leave scorch marks.

The system is designed from the ground up to operate perfectly by itself. External fans do not help cooling, and actually can hinder it by changing the airflow and static pressure in the case

There is never any reason to use them

Hello Corey

My name is Jonny and I will be assisting you today!

First, thank you so much for contacting us regarding your inquiry/ concern.

Short answer, no.

However, if you need to open up the console's shell and access the insides, it would void the warranty. Any attachments that simply plug into the ports on the Xbox will not.

FYI, doing this could possibly void a warranty, as the warranty states it can be voided if you operate the system outside recommended paramaters, and using any external cooling method is specifically declared operating outside the paramaters. Even using
the intercoolers you can buy in stores can void warranty.

Do not use any external or otherwise third party coolers on your console

The airflow is specifically designed to use the included fan, which is adequate for the system's needs. At best you're doing nothing, at worse you're sabotaging the built in cooling

These coolers can also void your warranty

If it's that hot, you should invest in an air conditioner rather than console cooling