I received my Flex 6400M/AT 3/31/18my ATU has never worked and never heard the fan com on.Thanks

Richard 1st thing to do after your rig is ready to go is touch the number on the touch screen below the menu box immediately below the words rf pwr this indicates what your power is set at but if you touch it a panel opens on the screen.

Immediately below the MON box on the left side you will see a box with atu mem in it touch that box so it is selected (background is lit light gray) Now touch the black area around the rf pwr word and the panel closes to your normal screen. Now press menu then press the transmit tab and another panel opens. At the top you will see Tune Power set that to either 10 or 15 then press exit on the left to go back to normal screen.

Using 20 m band tune to 14.240 with the vfo and use usb mode selected. With a dummy load connected to your selected transmit antenna or an antenna connected to it press very quickly the ATU button just like you were pressing a button to turn on a monitor quick press do not hold it in. You should hear some clicks as now the tuner is doing a new tune cycle when the clicks stop shouldnt take long you should see that the ATU button is now green which indicates the tuning operation was a success. If the button is not lit green after this it means the tuner could not find a match for your connected antenna and ended by placing the tuner in bypass mode or the tuner did not find a good match within its parameters. In any case you should hear the clicks while it is trying to match unless your swr is over 3:1 at start or below the parameters for a good match in which case the light would still be white because it ended in bypass mode and most likely no clicks would be heard.

The only way to reset the ATU memories is by a reset to factory defaults.

All the above info can be found on pages 76, 77 and 78 of the 6400M/6600M User Guide version 2.1.30 dated 29 January 2018 available on the dowload page under Flex 6000 signature series.

Hope this helps you test it and get it working.