I'm using an Anet A8 with Marlin 1.1.6.
I've read countless guides on PID auto-tuning and never saw that the fan needed to be on, but when I look at the Marlin source code's ANet A8 configuration (here: example_configurations\ANet\A8\Configuration.h) it states:
...
// ANET A8 Standard Extruder at 210 Degree Celsius and 100% Fan
//(measured after M106 S255 with M303 E0 S210 C8)
#define DEFAULT_Kp 21.0
#define DEFAULT_Ki 1.25
#define DEFAULT_Kd 86.0
#endif // PIDTEMP
So, should activate the fan before running the auto-test if I wish to update the PID values in Marlin for my Anet A8?