Genuine Dyson DC40 Yoke cable wiring assembly

When would this part need replacing?
-When the brushbar won't spin even after clearing the obstruction and pressing the reset button.
- When the white wire has visibly snapped after taking the Dyson apart.

Will fit the following Dyson DC40 models:
DC40 Animal, DC40 Animal Complete, DC40 Animal Exclusive, DC40 Multi Floor, DC40 Multi Floor Complete, DC40i

Genuine Dyson DC40 yoke cable wire assembly 923188-01