Extruder 2 won't heat/pin 8. Am I missing something?

Hi.

I purchased one of those core xy dual extruder printer kits off of ali-express. Very little instructions - particularly on the electronics. It was cheap. I plan to do a review when I get it working, but I can't get extruder 2 to heat. I can select heat on repetier-host, and get the time out cause the heat doesn't work. I can also select heat in the printer menu (not connected) with the same symptoms. Here is what I know it is not:

1) It isn't the arduino. (mega clone). I have several, and swapping them doesn't make a difference.
2) It isn't the power. I get 12 volts at both sides of D8.
3) It isn't the thermistors. They register changes in temperature appropriately.
4) It isn't the heat cartridge. Swapping with d10 heats extruder 2 properly.

BTW, this is ramps 1.4, and I am running the latest version of Repetier firmware. I have tried specifying pin 8 instead of heater 2 in the settings, and this makes no difference. I get no voltage on the arduino physical pin 8 in the circuit, no LED, and no power to the extruder. I am ordering a new ramps board, but in the meantime, I am wondering if there is some jumper or something I'm missing in software configuration.

Thanks if anyone can help...

-Don

Continuing to troubleshoot: I removed the Mosfet. Pin 8 is not shorted to ground, and shows the proper 10 ohms across R15. Still no voltage on pin 8 when selecting heat for extruder 2. Pin definition is correct in configuration.h.

#define EXT0_HEATER_PIN 10
...
#define EXT1_HEATER_PIN 8

(I specified physical pins as part of the debugging process).

-Don

Found the problem. It was partially dyslexia. I was on pin 9, and not pin 8. (I reversed them in the first post, but not on the board. I kept them reversed on the second post cause I didn't want to admit it, and it could have been true.) My troubleshooting was all correct - it was software. Many systems use pin 9 for the print cooling fan, and that default was in the config file, but not by pin number - just as default_fan_pin or the like. 2 assignments to one pin made them unusable. Disable the default_fan_pin and bingo - extruder heats. (Almost 6 hours of crap to find that out. Hope this post can help someone avoid those 6 hours.)