How To Diagnose Power Supply Problems

These are some symptoms that may be caused by the power supply. Other components may also cause these same symptoms, check the general diagnosis page for more information.
Symptom	Check Click on underlined items for further information
It makes a squealing or other loud noise	The power supply fan is failing and needs replacement. In most cases, the entire power supply must be replaced.
Nothing happens when I turn on the PC	Check that it is securely plugged into the outlet and into the back of the PC. Check that the outlet has power. Check for a second power switch near the power supply. The main power switch has failed and needs to be replaced. The power supply has failed and needs to be replaced.
The PC freezes before the [color:3224=blue ! important][color:3224=blue ! important]operating [color:3224=blue ! important]system starts loading	If the power supply does not supply the proper, stable voltages to the various components it may prevent the PC from starting. The voltages can be tested with a multimeter.
The PC randomly shuts itself off	The power supply could be overheating, check that the fan is working. The power supply could be failing. See also your BIOS and [color:3224=blue ! important][color:3224=blue ! important]Control [color:3224=blue ! important]Panel power settings.