IDLER GP-FRONT 8V2391 - Caterpillar

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Armature Short Circuit Check (3) Armature. (4) Growler tester.
Place armature (3) on growler tester (4). The tester needs to be turned to the ON position.
Hold a hacksaw blade against the armature core. Slowly rotate the armature while the blade is against the core.
The blade should not vibrate or the blade should not be attracted to the armature core.
If the blade vibrates or the blade is attracted to the core, the armature has a short. The armature must be rebuilt or replaced. Armature Ground - Test
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Armature Winding Ground Test (3) Armature.
Place the multimeter in the "20M" position. Touch one meter lead on each commutator bar and the other lead on the armature core.
Each multimeter reading should be greater than 100,000 ohms. A meter reading of "0.10" or a value that is greater is acceptable.
If the meter reading is lower than 100,000 ohms, the armature is grounded. The armature must be rebuilt or replaced. Armature Continuity - TestSpecial equipment is needed to test the armature for an open. If the commutator is pitted or the bars are burned, the armature has an open. The armature must be replaced.Armature Runout - Check
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Armature Runout Check (5) Commutator.
Check the runout of the armature (TIR) of the commutator (5). The maximum TIR that is allowed is 0.05 mm (0.0020 inch).
If the TIR is too great, the armature must be replaced. Commutator Outside Diameter - Check
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Commutator Outside Diameter Check (5) Commutator.
Check the outside diameter of commutator (5). The new diameters of the commutator and the minimum diameters of the commutator are provided in the Specifications section.
If the armature is worn, the armature must be replaced.
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Depth Of Segment Mica (X) Depth of segment mica.
Measure the depth of commutator segment mica. The minimum depth should be 0.20 mm (0.008 inch).
Keep all parts clean from contaminants.Contaminants may cause rapid wear and shortened component life.
If the depth is under the minimum, the mica can be undercut. If the mica is undercut, remove all shavings and mica particles. Brush Holder - Test
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Brush Holder Insulation Test (6) Brush holder plate. (7) Brush holder. (8) Brush spring.
Check the brush holder springs (8) for damage or rust. If necessary, replace the brush holder springs.
Place the multimeter in the "20M" position. Touch one meter lead to each positive brush holder (7) and the other lead to brush holder plate (6). Check both positive brush holders.
Each multimeter reading should be greater than 100,000 ohms. A meter reading of "0.10" or a value that is greater is acceptable.
If the meter reading is less than 100,000 ohms, the brush holder is grounded. The brush holder must be replaced. Brush Length - Check
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Brush Length Measurement (X) Brush Length.
Measure brush length (X) for wear. The new brush lengths and the minimum brush lengths are provided in the Specifications section.
If the brushes are worn below the minimum length, replace the brush holder and starting motor case. Overrunning Clutch - Check
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Overrunning Clutch Check (9) Housing