Hi folks,
I want to do the following to have extruder fan switch on/off based on temperature.
I have the standard ramps/arduino layout of D8/extruder, D9/fan, D10/bed.
I've read the ramps/arduino etc docs and think I have the right pin but just want a
doublecheck.

#define D9_PWM_OC2B 18 <<< is this the right pin?

// Extruder cooling fans
// Configure fan pin outputs to automatically turn on/off when the associated
// extruder temperature is above/below EXTRUDER_AUTO_FAN_TEMPERATURE.
// Multiple extruders can be assigned to the same pin in which case
// the fan will turn on when any selected extruder is above the threshold.
#define EXTRUDER_0_AUTO_FAN_PIN D9_PWM_OC2B // -1 replace -1 with D9_PWM_OC2B to test autofan control
#define EXTRUDER_1_AUTO_FAN_PIN -1
#define EXTRUDER_2_AUTO_FAN_PIN -1
#define EXTRUDER_AUTO_FAN_TEMPERATURE 50
#define EXTRUDER_AUTO_FAN_SPEED 255 // == full speed

Many thanks,
Andrew

Isn't D9 not simply pin 9?

Have you tried:

#define EXTRUDER_0_AUTO_FAN 9

Hi enif,
Actually I did yesterday, now it works like a charm.
I was getting confused between the physical pin and
the logical pin. Plus fan_pin or pin_fan having to be disabled
was a problem.
It's been a very long time since I've read any technical doc's
is my excuse.

Thanks Enid,
Andtew