Hi! FlashForge Creator Pro owner here, board VSF7.7.

Right extruder prints great; left extruder not at all. See below for all the tests I have done to try to diagnose the cause. At this point I feel all the mechanicals are working and it's coming down to logic boards, but I don't know what / how to test next.


1. In Load/Unload Filament - motor does not advance
2. In printing from left extruder, filament does not come out.


TESTED:
A. Nozzle is clear. I can push filament through when it is hot OK
B. Teeth are in great shape, unclogged and perfectly aligned with the "V" on the guide wheel.
C. Stepper motor is functional. I can perform the LED test on both pairs of leads and LED lights up when motor is turned
D. Stepper cable is OK. I tested continuity on all 4 wires and they are fine
E. Connectors are fine. They are all well-seated.
F. Test voltage to Stepper Driver board. 5.0V when machine is powered ON


FAILED:
* Set left extruder to "Unload Filament". Test voltage across both pairs - 0V


What should I do next?


Thank you for your ideas!