My iPhone 4S recently developed a problem with its volume control buttons. Magically, all by itself, the iPhone's volume setting would change. My fingers wouldn't be anywhere near the volume buttons but the volume would suddenly adjust, as if some ghost was pushing the buttons. It affected both the ringer volume and the music volume. I'd be walking along with earbuds on and the volume would suddenly drop to zero. WTF?!
A little research on the web revealed that it's a somewhat common problem. There are numerous related topics over in Apple's forums. What I learned is that it's a mechanical wear issue inside the volume button assembly. The backside of the volume buttons press against a flex pad that has traces for the volume control circuit. The volume buttons are kept separated from the flex pad by a spring. Over time, the edges of the spring wear through an insulative coating on the flex pad, thus intermittently closing the circuit and causing the volume level to change. It can affect either volume button, or both.
To fix the problem, Apple's engineers designed a little shim that slips in-between the flex pad and the spring, restoring the layer of insulation.
Quick and Inexpensive Repair!
I made an appointment with a Genius at my local Apple Store. The Genius was easily able to replicate the problem (the ringer volume started adjusting on its own while I was turning off the passcode for the phone). I was a little disappointed when I was told my iPhone was too far out of warranty for the repair to be done for free. But my disappointment evaporated when the Genius told me the total cost of the repair (placement of the shim) would be $6.00 (including sales tax)! The repair was completed in 20 minutes and the volume button demon has been exorcised from my iPhone 4S, hopefully for good!
By the way, somewhere along Apple's iPhone 4S production cycle, the shim apparently became a standard part of the volume control assembly. Later model iPhones shouldn't be as prone to developing the problem.
It's been a week since the Apple Store installed the volume control shim in my iPhone. Prior to the repair, my iPhone 4S volume would adjust by itself multiple times per day. Since the installation of the shim the volume control has functioned normally. I'm confident the shim is the definitive fix for this particular problem.