I have just purchased a second new D RTK-2 base unit.
On power up, there is no fan running within the unit, but my orginal unit does.
Is this a likey fault?, or someting else?

Hi, there. Sorry for your inconvenience. Whether the fan will be turned on is determined according to the ambient temperature and the drone's temperature. It may not be turned on if the temperature is not high. If the fan has cannot be turned on under any conditions, it is recommended to send it back for further testing.