You may need to remove some screws or panels to access the motor area.

This is usually located under the seat or at the base of the unit. However, if you have the necessary skills and knowledge, follow these general steps to fit a carbon brush to a Stannah 420 stair lift:

If you are not familiar with stair lift maintenance and repair, it's best to contact a professional technician or Stannah service representative to ensure the proper installation and safety of the carbon bush. Installing a carbon bush on a Stannah 420 stair lift requires some technical knowledge and experience, as it involves working with electrical components.