Starting/Charging Systems (H4SO): Generator: Inspection: Brush

Measure the length of each brush. Replace the brush if wear exceeds service limits. There is a service limit mark (A) on each brush.
Brush length:
- 2.5 L model
  Standard (1)
  
  18.5 mm (0.728 in)
  
  Limit (2)
  
  5.0 mm (0.197 in)
- 3.6 L model
  Standard (1)
  
  22.5 mm (0.886 in)
  
  Limit (2)
  
  5.0 mm (0.197 in)
Fig 1: Identifying Service Limit Mark On Brush
Courtesy of SUBARU OF AMERICA, INC.
Using a spring pressure indicator, push the brush into the brush holder until its tip protrudes 2 mm (0.08 in). Then measure the pressure of brush spring. If the pressure is 2.648 N (270 g, 9.52 oz) or less, replace the brush spring with a new part. 4.609 - 5.786 N (470 - 590 g, 16.58 - 20.810 oz) pressure is required on the new spring.

Fig 2: Measuring Pressure Of Brush Spring
Courtesy of SUBARU OF AMERICA, INC.