How to Troubleshoot the Power Supply Unit (PSU) of a Dell Desktop Computer

A faulty power supply can cause a system failure in one of two ways. It may not provide power to the system at all or it may not provide sufficient voltages and/or current to the various components of the desktop computer. The following step by step checklist helps identify if the power supply unit is working correctly.
 

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Determine if there is any sign of power at all

• Are the LED lights turned on? Check the power button, diagnostic LEDs, and HDD activity LED.
• Are there other signs of power such as fan spinning or disk drive activity?

If there are no signs of power at all, check the following:

1. Is the power cord plugged into the back of the system and into a known working power source? It is important to bypass any power strips, surge protectors or UPS units by making sure the power cord is plugged directly into a known good wall outlet.
2. Is the voltage selector correctly set for local power? Some power supplies are auto-switching and do not have a physical switch. For those that do, make sure the power cord is unplugged and flip the switch back and forth; again making sure it is set to the proper voltage. Plug the power cord in and test.
3. If there is still no sign of power, the next step is to isolate the power supply as much as possible. Make sure the power cord is unplugged and disconnect the power leads from all devices except the motherboard.
4. Any power leads to the motherboard should be reseated to ensure a good connection.
5. Remove memory, expansion cards and disk drive data cables to insure they are not causing the failure. These components would need to be removed later to complete no POST troubleshooting anyway if the power supply is not at fault.
6. If appropriate to the system model, test the I/O panel.
7. If there are still no signs of power at this point, it is most likely the power supply is non-functional. If there are indications of power, continue troubleshooting to isolate the failed component. 

If there are indications of power such as a blinking amber power LED, a solid amber LED, fan spin, or disk drive activity:

1. Bypass any power strips, surge protectors or UPS units by making sure the power cord is plugged directly into a known good outlet.
2. If the system fails to power up correctly and attempts POST, the next step is to isolate the power supply as much as possible. Make sure the power cord is unplugged and disconnect the power leads from all devices except the motherboard.
3. Any power leads to the motherboard should be reseated to ensure a good connection.
4. Remove memory, expansion cards and disk drive data cables to ensure they are not causing the failure. These components will need to be removed later to complete no POST troubleshooting anyway if the power supply is not at fault.
5. If the system fails still fails to power up correctly and attempt POST at this point, it is most likely the power supply is non-functional and should be replaced. If however, the power LED is solid amber, the failure could potentially be the motherboard and Technical Support involvement may be required.
6. If there are indications of power, continue troubleshooting to isolate the failed component.  Our articles Computer Does not Turn on or go Into Windows  or Resolve No Power, No POST, No Boot or No Video issues with your Dell Computer  can provide additional troubleshooting to help.

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Perform a self-test on the power supply unit

Dell Inspiron, XPS, OptiPlex, Precision and Vostro desktop systems include a power supply with a built in self-test (BIST) feature that helps diagnose the health of the power supply unit. The LED indicator on the PSU helps identify if the power issue is caused by the power supply unit.

How to run the self-test using the button on the PSU

1. Turn off the computer.
2. Press the BIST button on the computer and check whether the LED lights up.
3. The light should be solid on not flickering or flashing and the power supply fan should also turn on to speed. If the fan is not spinning up properly this should be considered a BIST failure even if the LED lights up.

• If the built-in self-test LED turns on, then the power supply unit is able to deliver power to the system board.
• If the BIST LED does not light up, then the power supply is not able to deliver power to the system board and could be caused by any component connected to the power supply or the power supply itself. The next step would be to isolate the source of the power failure by disconnecting parts from the PSU, see the Dell knowledge base article Resolve No Power, No POST, No Boot or No Video issues with your Dell Computer.

How to run the self-test without the button on the PSU

1. Turn off the computer.
2. Disconnect the power cord from the PSU, and wait for 15 seconds.
3. After 15 seconds, connect the power cord back to the PSU.
4. The LED light should stay on for 3 seconds and then turn off.

• If the built-in self-test LED turns on, then the power supply unit is able to deliver power to the system board.
• If the BIST LED does not light up, then the power supply is not able to deliver power to the system board and could be caused by any component connected to the power supply or the power supply itself. The next step would be to isolate the source of the power failure by disconnecting parts from the PSU, see the Dell knowledge base article Resolve No Power, No POST, No Boot or No Video issues with your Dell Computer.

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 General information and troubleshooting articles can be found on the AC Adaptor support page.

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