Stepper's with eight leads can be wired in Series or Parallel. If it is miswired, a motor fault will result.
Here is one example...
Eight leads:
A+ A+ lead
Act+ A+ center tap
Act- A- center tap
A- A- lead
B+ B+ lead
Bct+ B+ center tap
Bct- B- center tap
B- B- lead
When wired correctly in Series, each of the leads will go to the appropriate pins on the motor connector of the drive. The A+ and A- center taps will be connected to each other. So will the B+ and B- center taps be connected to each other.
If one of the phases has a center tap and its corresponding lead swapped, a motor fault can occur. For example, if A+ and Act+ are swapped, the motor's phase will still measure correctly when you measure the resistance from A+ to A-. However, the drive does not like this.
