There is no 14V connector. The power supply has 12 V and that’s where the fans are connected.
The fans I bought have a temperature sensor, that has to be attached anywhere in the power box (best where the temp. is highest). If a certain temp is reached the fans will turn faster in order to increase the cooling effect. As soon as the sensor recognizes that the temp has fallen under the limit the fans turn slower again.
That’a all….no witchcraft… ;-)