External hard drive cables rarely fail unless they get the same sort of abuse. USB cables can fail after prolonged use, though this is more likely to happen to the Micro USB cables used with mobile phones. EHDs that have their own power supplies tend to work more reliably. This can be a problem if the PC’s motherboard does not supply enough power to the USB port you are using or if the drive is plugged into a non-powered hub. Some external hard drives draw their power from the USB port and they may not get enough. The port, the connecting cable, the power supply and the external hard drive (EHD) can all suffer from physical and/or electrical faults.