Setting up an RS Components 8-wire Stepper

I had similar problems with some steppers I bought, the colour codes did not match the docs so one phase-pair was back to back, so that they cancelled each other out.

You have to hope that the pole-pairs are right, though.

It is helpful to have a current-limited power supply, but you can make some useful deductions just by touching wires together and trying to turn the motor by hand.

First find the ends of each winding, and make a note. If you touch two wires together and the motor gets harder to turn, then they are a pair. If there is no change, then they are not a pair.

Next find out which are the + and - ends of each winding. If you put + to + and - to - on two windings from the same phase then the motor will turn freely, if you put + to - and - to + then the motor will get stiff (about twice as stiff as the earlier test). + and - is entirely nominal, all that happens if you guess wrong is that the motor spins the wrong way, and that can be fixed in software. Label the wires.

You will need to trust the docs as to which sets of windings make up a phase.

You then need to decide how you want to wire the motor. Are your drives unipolar or bipolar? Do you want torque or speed?

Unipolar (6-wire) and bipolar-series (4 -wire) (higher torque for the same current, lower speed for the same voltage) you need to permanently link one + and one - of each phase pair together. That become "common" on a unipolar drive, or should be joined, insulated and tucked away for bipolar drive. For bipolar parallel drive join + to + and - to - for each phase. With either bipolar setup the 4 ends are A+ and A- of one phase, and B+ and B- of the other.