37-MT, 41-MT, and 42-MT Series Starting Motors Caterpillar

Brush Holder Test

Illustration 1	g00800898
Typical example of a brush holder test (6) Brush spring (7) Brush holder (8) Brush holder plate

1. Check the brush springs (6) for damage or rust. If necessary, replace the brush springs.

2. Place the multimeter in the "20M Ohms" range. Touch one meter lead to each positive brush holder (7) and the other lead to brush holder plate (8). Check the three positive brush holders (7).

3. Each multimeter reading should be greater than 100,000 Ohms. A meter reading of "0.10" or a value that is greater is acceptable.

4. If the meter reading is less than 100,000 Ohms, the brush holder is grounded. The brush holder must be replaced.

Brush Length Check

Illustration 2	g00801226
Typical example of a brush length measurement (X) Brush length

1. Measure brush length (X) for wear. The new brush length is 23.0 mm (0.91 inch). The minimum brush length is 10.0 mm (0.40 inch).

2. If the brushes are worn below the minimum length, replace the brush holder.