You need to use a 30-pin to firewire cable and charger, or an iPod dock. The 3rd gen iPod can’t charge with a USB cable like the other iPods can.
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Are you trying to charge it via USB? You need to use a 30-pin to firewire cable and charger, or an iPod dock. The 3rd gen iPod can’t charge with a USB cable like the other iPods can.