That motor is 4.2A in unipolar and 3A in series and 6A in parallel.
If you are connecting it is parallel and only giving it 4.2A, you are under powering it.


Quote Originally Posted by Robin Hewitt View Post
Possibly right

I'm sitting looking at the motor spec sheet and it shows parallel as 4.2A/phase, but series as only 3A per pair. Sounds illogical

If I knew what "hybrid" meant it could explain it...

...perhaps