Starting System & Charging System (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:

Service limit (1)

5.0 mm (0.197 in)

Standard (2)

18.5 mm (0.728 in)

Fig 1: Identifying Length Of Brush
Courtesy of SUBARU OF AMERICA, INC.
Check that there is appropriate pressure on the brush spring.
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 2.2 N (0.224 kgf, 7.91 oz) or less, replace the brush spring with a new one. 4.8 - 6.0 N (0.489 - 0.612 kgf, 17. 26 - 21.58 oz) pressure is required on the new spring.

Fig 2: Checking Brush Spring For Proper Pressure
Courtesy of SUBARU OF AMERICA, INC.