Nees help configuring RRD fan extender in my i3V8....

[printbus]

I don't have a fan extender, and don't even use Marlin and RAMPS anymore, but rather than let you hangin... Anyone else is welcome to jump in.

There's nothing you have to do to tell firmware you have an extender. The extender simply acts as a buffer - as long as the Marlin pin mapping is correct, wiring is correct and the board is functional, things should work.

To clarify, the servos header provides access to the D11, D6, D5, and D4 Arduino pins. The Geetech appears to "normally" buffer the D11 and D6 outputs. You've got the ABL servo on D11, so there's a conflict. Moving the fan extender up one pin on the header moves it so it is connected to the D6 and D5 outputs on the Servos header instead of D11 and D6, freeing up access to D11 for the ABL servo. If you move the fan extender that one pin, you'd have to have the print fan (FAN_PIN in pins.h) configured to use either D6 or D5, the next pins on the servo header. If you move the Geetech extender up two pins (which I think some people have done simply to leave D6 as another available pin), the fan extender will be buffering outputs D5 and D4 on the servos header, and FAN_PIN needs to be defined as one of those.

What can be confusing in pins.h is that for your motherboard type, any given function should only be defined once, and any given pin can only be used once. What motherboard type (33, 34, etc.) are you using and what was the pin number involved in the same pin number compiler error? That might provide some insight.

Have you double checked the 12V connection to the fan extender? The instructables link has some scary information about how the Geetech wiring diagrams has the polarity backwards...

FWIW