Alternator - Delco 21SI Caterpillar

Illustration 1	g00720928
(1) Slip rings (2) Rotor (3) Rotor shaft

Field Winding Continuity Test

1. Set the multimeter to the 200 ohm resistance scale. Measure the resistance between the slip rings (1) .

2. The resistance between the slip rings (1) should be within the following values.

   Resistance of field winding at 27 °C (81 °F)

   9X-6796 Alternator Gp ... 1.7 to 1.8 Ohms

   9X-9096 Alternator Gp ... 1.7 to 1.8 Ohms

   121-4134 Alternator Gp ... 1.7 to 1.8 Ohms

   121-4135 Alternator Gp ... 1.7 to 1.8 Ohms

   113-1379 Alternator Gp ... 1.7 to 1.8 Ohms

   125-9597 Alternator Gp ... 1.7 to 1.8 Ohms

   107-7977 Alternator Gp ... 9.5 to 10.7Ohms

   132-2156 Alternator Gp ... 9.5 to 10.7Ohms

3. Replace the rotor (2) if the measurement is incorrect.

Field Winding Ground Test

1. Set the multimeter to the 20 M ohm resistance scale. Measure the resistance between one of the slip rings (1) and the rotor shaft (3) .

2. The multimeter reading should be greater than 100 K Ohms(0.100 M Ohms).

3. Replace the rotor, if the multimeter reading is low. Low resistance indicates undesired continuity between the field winding and the rotor shaft.

4. Repeat steps 1 through 3 for the other slip ring (1) .