Charging System: Generator: Inspection

Standard exposed brush length: 

10.5 mm (0.413 in.) 

Minimum exposed brush length: 

4.5 mm (0.177 in.) 

If the exposed brush length is less than the minimum, replace the brush holder.

Fig 1: Measuring Exposed Brush Length Using Vernier Calipers

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1. Using an ohmmeter, measure the resistance between the slip rings.

   Standard resistance: 

   2.3 to 2.7 Ω at 20°C (68°F) 

   If the resistance is not as specified, replace the rotor.

   Fig 2: Measuring Resistance Between Slip Rings Using Ohmmeter

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1. Using an ohmmeter, check the resistance between the slip ring and rotor.

   Standard resistance: 

   10 kΩ or higher 

   If there is continuity, replace the rotor.

   Fig 3: Checking Resistance Between Slip Ring & Rotor Using Ohmmeter

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1. Check that the slip rings are not rough or scored.

   If rough or scored, replace the rotor assembly.

2. Using vernier calipers, measure the slip ring diameter.

   Standard diameter: 

   14.2 to 14.4 mm (0.559 to 0.567 in.) 

   Minimum diameter: 

   14.0 mm (0.551 in.) 

   If the diameter is less than the minimum, replace the rotor.

   Fig 4: Measuring Slip Ring Diameter Using Vernier Calipers

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If necessary, replace the generator rotor assembly.

Fig 5: Inspecting Generator Rotor Bearing

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If necessary, replace the bearing.

Fig 6: Identifying Generator Drive End Frame Bearing

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