Only 5V works

In itself, the adapter does exactly what it should, namely provide connectors for fan ready.
I once measured by the voltmeter and by the following assignment found out (until now she had no one actually written):

Black: 12 Volt
White: 5 Volt

Interestingly, none of the works I tested fan at 12V Power Supply (no jerking, no turning even when triggers the fan). Why this is, however, is beyond me, because I have been measured, there are even 12 volts.
I have tested on two power supplies and work for two only fans that are plugged into the 5V connections.

Conclusion: I'm going to use the adapter anyway, because I need only the two 5 volt connections and that's still cheaper than buying two 5 volt adapter.