RAMPS Z only one direction, extruder doesn't heat

Here's my setup:

Reprap Prusa, RAMPS 1.4, Arduino Mega 1280, Makergear Hot End, OSX host (Lion)

The only firmware and software combo I've got somewhat working is Sprinter + ReplicatorG. I can jog X and Y and E in both directions and it does read the temp correctly, but it only lets me jog Z in one direction and the extruder heater won't come on.

The Z motors are wired correctly, they work correctly with the RAMPS test sketch, and the endstops are wired correctly. Before I had them wired up, all three axes would only jog in one direction.

For the extruder heater, it's not a wiring issue because it heats up fine if I attach it directly to a 12V battery. The thermistor tracks it perfectly and it extrudes really nicely, but the onboard D10 won't run it. I've checked it with a multimeter after setting the temp to 100C and the little indicator LED on the corner of RAMPS comes on but there's no voltage coming out of any D10, D9, or D8.

Thanks!

One way direction only use to be caused by a missing connection or the absence of the end stop (or an error on your Configuration.h regarding that end-stop). Does Z-axis react to home button/command?

The little led on the corner of RAMPS 1.4 is for the fan (if I remember correctly). Sprinter does lit the green power led once the heater is on. If the green led is lit and no heat happens then it might be that the corresponding Mosfet is broken (assuming all soldering job is ok)

misan