After verifying ownership and completing troubleshooting, a DELL-Cares agent setup service.
When power cable plugged to my Dell Optiplex 7070 SFF, the fan runs with full speed with huge noise. After pressed the power button to start OS, the fan become normal. After shutdown the OS, the fan runs with full speed again till I unplug the power cable. I cannot stand the noise, how to solve it ?  
How to solve that fan runs with full speed when power cable plugged