For KRC4 is the same variable and you can also find on the manual for KR4 System Variables.
$CAB_FANSPEED = Speed of the cabinet fan (external fan)
$PC_FANSPEED = Speed of the PC fan (internal fan)
It is located on $OPERATE.dat, that's a protected system dat.
INT $PC_FANSPEED
INT $CAB_FANSPEED
You can load in a INT data and work with it.