The power supply fan does not spin when the computer is powered on or while running ePSA diagnostics. This issue is noticed on the following Dell computers:
Power supplies on these select Dell computers have a new feature to ensure that the computer runs as quiet as possible.
If the computer is using 15% or less power from the power supply, the fans in the power supply are designed to shut off to ensure lower noise levels. The computer will continue to operate normally and will not cause the power supply to overheat.
If the computer uses more than 15% power from the power supply, the fans in the power supply will turn on and spin at an appropriate speed to ensure proper operating temperature.
To verify if the power supply is functioning normally, press the built-in self test switch on the power suppluy (Figure 1). If the LED turns on, the power supply is functioning normally. If the LED is off when you press the built-in self test switch, contact Dell Technical Support.
Figure 1: Built-in self test switch for power supply