JF Series Starting Motor Caterpillar

Armature Short Circuit Test

Illustration 1	g00719333
Armature short circuit check (3) Armature assembly (A) Armature Testing Gp

1. Place the armature assembly (3) on the Armature Testing Gp (A). Turn on the tester.

2. Hold a hacksaw blade against the armature core. Slowly rotate the armature.

3. The blade should not vibrate. The blade should not be attracted to the armature core.

4. If the blade vibrates or if the blade is attracted to the core, the armature assembly has a short. The armature assembly must be rebuilt or replaced.

Armature Ground Test

Illustration 2	g00719338
Armature winding ground test (3) Armature assembly

1. Put the Digital Multimeter on the "20M" resistance scale. Touch one meter lead on a commutator bar and the other lead on the armature core.

2. Each reading should be greater than 100,000 ohms.

3. If the meter reading is lower than 100,000 ohms, the armature assembly is grounded and the armature assembly must be rebuilt or replaced.

Armature Continuity Test

Testing for an open circuit in the armature is difficult without special equipment. If the commutator shows signs of pitting, the armature assembly has an open circuit and the armature assembly must be replaced. If any of the commutator bars are black, the armature assembly has an open circuit and the armature assembly must be replaced.

Armature Runout Check

Illustration 3	g00719349
Armature runout check (4) Commutator (5) Core

1. Check the armature assembly runout (TIR). The maximum indication that can be measured is given below:

   (4) Commutator ... 0.03 mm (0.001 inch)

   (5) Core ... 0.10 mm (0.004 inch)

2. If the armature assembly runout is greater than the values above, the armature assembly must be replaced.

Commutator Outside Diameter Check

Illustration 4	g00719352
Commutator outside diameter check (4) Commutator

1. Check the outside diameter of the commutator (4) with the Dial Caliper As. The diameter should have a value:

   New diameter ... 45 mm (1.77 inch)

   Minimum diameter ... 42.5 mm (1.67 inch)

2. If the armature assembly is worn, the armature assembly must be replaced.

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Illustration 5	g00720043
Depth of insulation between commutator bars (X) 0.8 mm (.03 inch)

3. Measure the depth of insulation between the bars of the commutator (4). The minimum depth (X) should be 0.8 mm (0.03 inch).

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NOTICE
Failure to remove the insulation shavings and particles will cause the brushes to wear at a fast rate.

4. If the depth is under the minimum, the insulation must be undercut. If the insulation is undercut, remove all shavings with forced air and remove all insulation particles with forced air.