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[ The PC Guide | Troubleshooting and Repair Guide | The Troubleshooting Expert | Troubleshooting Specific Components | Troubleshooting the System Case | LEDs or Case Buttons ]

The hard disk LED does not show any activity even though the disk is working properly

Explanation: The hard disk LED does not flicker when the hard disk is being accessed, although the hard disk is working properly.

Diagnosis: If this is a system that was just put together, then the LED was probably connected incorrectly. On an existing system, the cable connecting the LED to the motherboard was probably jarred loose. The LED could also be burned out, although this rarely happens, even after years and years.


  • If the hard disk isn't working properly then you should follow this section instead.
  • Double-check the LED connection to the motherboard (or hard disk controller). Make sure the connection is solid.
  • Try reversing the leads on the LED connection and see if that fixes the problem.
  • Many motherboards have four pins for the hard disk activity LED, even though only two are needed for the LED. If it is not working then you may have connected the wires to the wrong two pins. Consult your motherboard documentation or try a different pair of pins.
  • If there is another LED that is working, such as the power LED, try temporarily swapping that LED connection with the hard disk LED wires. If when you do this the power LED (now connected to the hard disk activity signal) comes on but the hard disk LED doesn't light when the power comes on, then the hard disk activity LED is burned out. If the hard disk LED does work when the power comes on but the power LED is dark, then the problem is with the motherboard or hard disk controller card, which is not producing the correct signal.
  • Try to connect the LED to the hard disk LED output pins, if your hard disk has them and if the motherboard or controller isn't putting the right signal out.

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