For all of you who have this issue, the real reason is not something that Apple wants to admit. The problem is a defect in the manufacturing of older iPhone, not debris in the headphone jack, and might be limited to older generation devices (3G or older) using older manufacturing processes.

If you go into a retail store, Apple will first try to convince you that something stuck in the headphone jack is the real culprit and after 5-10 minutes in the backroom ‘cleaning it’ it will appear to be working again. Of course, this goes away in that time the ‘Genius’ is in the back room, since the device has cooled down. The option they present to you (if out-of-warranty) is to replace the old device with another old device at the cost of a newer generation device, which might very well exhibit the same behavior in the future.

The simplest way for you to reproduce this issue is by using your iPhone for phone calls or heavy game playing for extended periods of time (15+ minutes depending on the severity of your hardware issue) and the phone will switch into headphone mode automatically. This is extremely annoying if you’re on a call with a Bluetooth headset since it will switch by itself in the middle of your call to headset mode.

Usually it resolves itself shortly after the activity that caused the heat stops. Thus, by the time you arrive at a ‘Genius-bar’ appointment, it’s no longer repeatable. Or after gathering the q-tips/headphone plugs and inserting them repeatedly, the cool down will have happened and it appears to also resolve. But not matter what, repeated use will bring this issue back.

THE RESOLUTION: NONE at this time, unless we complain and highlight the repeatability of this issue. Apple has downplayed this as not being a hardware issue and will likely fight any requests for free replacements.