It´s really funny. Now the front fan 2 will seen as rear fan from the Intel Desktop Utiliities and this fan is going also down to 0 rpm. but the fan is running normally. After this the cpu fan is going up from round about 800 rpm with 1480 rpm. I think there is a big bug in the BIOS.
May be I have to use a Y cable for the two inlet front fan´s at front fan 1 connector. Then the Intel Desktop Utilities will see only one of the two fan´s. I´ll test this tomorrow.