@Greg Holloway the config file from the github repo doesn't seem to set up the default PCF (fan 0 in RRF parlance) per each tool. That means that M106 sent by your slicer won't do anything. Here's a fix: Code: ; Fans M106 P0 S0 ; UNUSED M106 P1 S255 H1 T70 ; T0 HE M106 P2 S0 ; T0 PCF M106 P3 S255 H2 T70 ; T1 HE M106 P4 S0 ; T1 PCF M106 P5 S255 H3 T70 ; T2 HE M106 P6 S0 ; T2 PCF M106 P7 S255 H4 T70 ; T3 HE M106 P8 S0 ; T3 PCF ; Tools M563 P0 S"T0" D0 H1 F2 ; Define tool 0 G10 P0 X0 Y0 Z0 ; Reset tool 0 axis offsets G10 P0 R0 S0 ; Reset initial tool 0 active and standby temperatures to 0C M563 P1 S"T1" D1 H2 F4 ; Define tool 1 G10 P1 X0 Y0 Z0 ; Reset tool 1 axis offsets G10 P1 R0 S0 ; Reset initial tool 1 active and standby temperatures to 0C M563 P2 S"T2" D2 H3 F6 ; Define tool 2 G10 P2 X0 Y0 Z0 ; Reset tool 2 axis offsets G10 P2 R0 S0 ; Reset initial tool 2 active and standby temperatures to 0C M563 P3 S"T3" D3 H4 F8 ; Define tool 3 G10 P3 X0 Y0 Z0 ; Reset tool 3 axis offsets G10 P3 R0 S0 ; Reset initial tool 3 active and standby temperatures to 0C Now whichever tool is active will have its PCF turn on when you issue a M106 without the fan number specified (e.g. T1, then M106 S255 will fire up PCF on the second tool, and if you do a swap with T0, the next M106 S255 will turn on the PCF on the first tool). This should also probably be commented out in tpostN.g: Code: ;PCF fan on M106 P2 S127 Also, this as well in tfreeN.g: Code: ;fan off M106 P8 S0 The reason why is that if there's a tool change within the same layer, and your slicer only sets the fan speed on layer change, you'll end up with the fan (unintentionally off) when you swap a tool.