Fan0 won't turn off

[zzing]

I have recently installed a Berdair with a flyback diode on the connector and it worked just fine until a couple of days ago I noticed that it turns on when the duet turns on.

I have switched the fan out for another and it turns on as well.

I noticed an older thread: https://forum.duet3d.com/topic/406/duet-wifi-fans-won-t-turn-off

I am wondering if I might have fried something and if it is fixable.

The only parts of my config related to fans:

M106 P1 H1 T75 S0.4
M106 P0 F25000

I saw it mentioned by dc42 somewhere that the mosfet could run the thing (its at 24V) so I decided not to put it on the 'eswitch' or an SSR.

I am running 1.0 or 1.01 of the duet wifi board (according to web interface), running on the latest stable (RTOS).0_1531835744782_config.g

[dc42]

There is another thread on this subject, more recent than the one you linked to. In summary:

Brushed DC motors (which is what air pumps normally use) draw a large surge current when they are powered up. I expect this surge current caused the fan output driver mosfet to fail. We recommend you either use a series thermistor to limit the surge, or else use an external mosfet switch that can handle the surge.