How to erase AirPort Extreme that doesn't show up

First of all, you don't need the AirPort Extreme to "show up" to completely reset the device.

You will want to do a Factory Default Reset (A Hard Reset will not completely wipe the stored network settings on the AirPort)

Power off the AirPort Extreme by pulling the power supply cord from the back of the unit

Wait 5-10 seconds

Hold in the reset button first, and keep holding it in while you plug the power cord back into the AirPort Extreme

Keep holding the reset button for another 7-8 seconds after you plug the power cord back in

Release the reset button

The AirPort Extreme will display a solid amber light for a few seconds then the light will turn to flashing amber

You are done. You can refer to Apple's Support document on resets if you need more info:

How to reset your AirPort base station - Apple Support

AirPort Extreme second generation ~2008 A1143 doesn’t have storage.

Here’s the reset procedure: How to reset your AirPort base station - Apple Support

You’ll be trying the hard reset.

If you’re not sure if it reset and if you haven’t changed your Wi-Fi password since its retirement, maybe change the Wi-Fi password.

eBay price for a working 2nd-gen ~2008 model looks to be around USD$15.

Bob Timmons wrote:

First of all, you don't need the AirPort Extreme to "show up" to completely reset the device.

You will want to do a Factory Default Reset...

You are done. You can refer to Apple's Support document on resets if you need more info:

How to reset your AirPort base station - Apple Support

Confusingly, "Factory-default reset, available only with firmware version 7.9.1 on AirPort Time Capsule 802.11ac and AirPort Extreme 802.11ac..." is referenced later in that same document, and this AirPort is too old for that.

Airport Extreme is a Wi-Fi router only......no hard drive on board.

It sounds as if you might be asking about a Time Capsule.....essentially an AirPort Extreme with a built in hard drive.

Please confirm on that before we proceed.

Might be confusing, but you can still perform a Factory Default Reset on any AirPort by using the same instructions to first power off the AirPort, then hold in the reset button before you plug the power back in and keep holding the reset button another 7-8 seconds.

Before posting, I confirmed this using an old 802.11n AirPort Extreme that has been here for probably 8 years or more.

A Hard Reset keeps a record of the last set of network settings, even though the current network settings are erased. So, using AirPort Utility a user could call up the last set up network settings. by using the option to restore from a previous setup.

Nice work!