Starting/Charging Systems (H6DO): Generator: Inspection: Brush

Measure the length of each brush. If wear exceeds the service limit, replace the brush. Each brush has the service limit mark (A) on it.
Brush length:

Service limit (1)

5.0 mm (0.197 in)

Standard (2)

18.5 mm (0.728 in)

Fig 1: Measuring Length Of Brush
Courtesy of SUBARU OF AMERICA, INC.
Checking brush spring for proper pressure
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 less than 2.2 N (224 g, 7 91 oz), replace the brush spring with a new one. The new spring must have a pressure of 4.8 to 6.0 N (489 to 612 g, 17.26 to 21.58 oz).

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