7 With the armature removed, you can see the brush holder and park switch. If your Mustang has been in a rainy climate, chances are the brushes are worn out and must be replaced. Brushes can be sourced at any electric motor supply store along with new springs. Armature slipper contacts should also be dressed and cleaned with fine-grain sandpaper, then thoroughly cleaned of debris. If slippers are excessively worn, you will need to replace or rebuild the armature. Just about any electric motor overhaul shop can rebuild your armature.