The cooling fan in my PWM capable DeepCool PSU is running at 100% all the time. How do I control the fan speed?

The DeepCool PWM capable PSUs are controlled by the intelligent temperature control feature that is built into the PSU. You would not be able to control the fan speed by traditional PWM signals from the motherboard. The fan will only spin at a lower speed when the power load and internal PSU temperatures are extremely low. Also, make sure the ambient temperature in the system is not too high.