Hi Rob,
Just in the thrones of sorting my soft top open close issues!!
First off, have you tested that it works or not? You access it under the plastic cover in the middle, behind your seats. There's a great photo heavy ' how to remove the 5th bow motor ' on the US 350z forum. It can be the brushes just need replacing. Simple procedure and could save you loads. Google.
You can test it in situ also by wires from the two terminals ( + and -) to see if it works independently, bugger to get at the terminals that way though.
Mine does work, but not functioning
following passenger seat forward, Windows down, click open latch then NOTHING!!
As well as Alex, Jon @ Emporer Tuning may be able to help.
Don't panic just yet!!
Still trying to sort mine!
Regards.