I used the Picture from https://duet3d.dozuki.com/Wiki/Duex2_and_Duex5_Features#Section_Jumpers and there is the wrong keying tab shown. sorry I was comparing the picture with the drawing thats it I thing then the picture wrong.

@dc42 said in Duex : inverted Fan Output Pins:

keying tab on the connector

I have a Sceenshot attached with the positions of the keying tab(nose for Molex) and the V_Fan Pin and they are flipped.

Re: Duex 2: Zero-Power to Fan Outputs.

I notice that the V_Fan Pin on the Duet WiFi and the Duex are inverted.
If you change a Fan from the Duet WiFi to the Duex you need to change the Pins from the Fan.