All USB connections detected as "AC" - Motorola Defy+

[defyplususer]

Until recently, I frequently used my Motorola Defy+ (running stock Gingerbread) for USB tethering and data transfer to a PC. But now whenever I connect the phone to a PC, the phone detects the connection as "AC", and the PC doesn't see the phone. I've tried several different USB cables (from different manufacturers), and two different PCs (running Windows and Linux), but the phone always thinks it's an AC charging connection. I'm also worried I might damage the PC, as I know the phone is supposed to draw more current from an AC charger than from a computer. Is this problem likely to be caused by a hardware fault in the phone's USB port, or by an Android settings problem? I've googled extensively and can't find anybody else with the same problem, though many users have the opposite problem (AC chargers being recognised as USB).

 

[friedtators]

Check your settings in android. You need to tell it to treat it as storage.

 

[defyplususer]

How can I enable USB storage if there is no notification when I connect the cable? (Is there an option somewhere in settings for Gingerbread, and if so where?)

I also tried enabling USB tethering, but the checkbox is greyed out with the words "USB not connected".

 

[defyplususer]

Following up on this, I am now reasonably convinced that my Micro USB port is damaged, although I cannot see any physical damage. One of the cables that I started using in the past few months is a cheap unbranded USB cable purchased from eBay, and it requires a slightly larger insertion force than other cables: not a huge force, but noticeably larger. I suspect that this cable has damaged the port, so that one (or both) of the data pins is not connecting, but the +5V and Ground pins are unharmed, so the port only works for charging. If this is true, I was unwise to risk damaging the phone with a cheap connector, since phones cost around 100 times more than USB cables.

Unless anybody has any alternative ideas regarding the cause of this problem, I will take the phone to a repair shop tomorrow.