How to activate extruder fan on disabled 2nd extruder

[flimshaw]

I noticed this at the very end of the notes for Replicator machines and clones: "When an extruder is disabled (i.e., not present), the firmware no longer manages its heatsink cooling fan. This has been done to aid users who wish to experiment with using the fan's control electronics for other purposes."

Is there a way to activate this fan with gcode? I have a rep dual and I have disabled and removed the left extruder in the hopes of repurposing its fan as a printbed fan. M106 doesn't work though, and I can't find anything obvious in the docs or source code. Thanks!

[SaschaKP]

I would like you to suggest to change the firmware in your printer, but that's up to you, I've also abandoned my current fork, since this piece of code is abandoned from almost 4 years. Use marlin, it works with mightyboard style machines.