How to Fix Apple Mighty Mouse Power Button

Firstly flip your mouse upside down and find the power switch. It is located just above the Apple logo and looks like a sliding door.

Slide the power switch to the off position or until it fully covers the optical sensor.

Locate the clip holding the battery cover on the mouse and use a sputter or your nail to push it aside to allow the door to spring up.

This can take a few attempts especially if your mouse is well used and trying different approaches may get it to open up. For mine I had to slightly push the door down to open it.

Once the door pops up remove it but keep it close.

The Mighty Mouse's on off switch works by the plastic slider on the door pushing down a bent piece of metal to then press a button on the main chassis of the mouse. (photo 1)

Over time the metal (photo 2) can bend to far down and not press the chassis button (photo 3) .

To fix this issue take a hard flat tool, a metal pry tool works well for this and pry up on the bent piece. If your battery door had issues popping open you can give the round bend piece (photo 3) the same treatment but don't put as much force as you could damage it.

Once it is raised a bit put the mouse back together to see if it works again or needs further prying. If there are still issues after a few bending attempts try cleaning the chassis side button and make sure it is pressing in. (photo 3, step 4)