GEAR-FUEL PUMP DRIVE 4W9987 - Caterpillar

Brush Holder Test
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Brush holder insulation test (6) Brush holder plate (7) Positive brush holder (8) Brush springThe positive brushes must be disconnected from the field winding leads in order to do this test.
Check the brush springs (8) for damage and for rust. Replace the springs, if necessary. Remove the positive brushes from the brush holder plate.
Put the Digital Multimeter on the "20M" resistance scale. Touch one meter lead to each positive brush holder (7) and the other lead to the brush holder plate (6). Check both positive brushes.
Each reading should be greater than 100,000 ohms.
If the meter reading is less than 100,000 ohms, the brush holder is grounded and the brush holder must be replaced.Brush Length Check
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Brush length measurement (X) Brush length
Measure the brush length (X) for wear. The length should be the following value:New length ... 15.5 mm (0.61 inch)Minimum length ... 8.5 mm (0.33 inch)
If the brushes are worn below the minimum length, the brushes must be replaced.