N3 Series Brushless Alternators Caterpillar

Illustration 1	g00867614
Field winding (1) Rear frame (2) Leads for the field winding (3) Field winding

The illustrations below show The N3 series alternator (35 amperes).

Field Winding Continuity Test

Illustration 2	g00867623
Field winding continuity test (2) Leads for the field winding (4) Lead for the rectifier

1. Remove the rear cover.

2. If the alternator has a capacitor, remove the capacitor.

3. Remove the regulator.

4. Connect the multimeter leads across field winding leads (2). This is shown in Illustration 2.

5. Measure the resistance between the field winding leads.

   Expected Results:

   N3 Series Alternators (50 amperes) ... 8 ± 1 ohms

   N3 Series Alternators (35 amperes) ... 12.9 ± .65 ohms

   Results:

   OK - The resistance is within tolerance. The field winding is normal. STOP.

   NOT OK - The resistance is above tolerance. The field winding has an open circuit. Replace the field winding. STOP.

   NOT OK - The resistance is below tolerance. The field winding has a short circuit. Replace the field winding. STOP.

Field Winding Ground Test

Illustration 3	g00867625
Field winding to ground test (2) Leads for the field winding (4) Lead for the rectifier (5) "B-" terminal

1. The rear cover, the capacitor, and the regulator remain removed from the alternator.

2. Connect one multimeter lead to the "B-" terminal. Connect the other multimeter lead to one of the field winding leads (4). This is shown in Illustration 3.

3. Measure the resistance.

   Expected Result: The resistance is greater than 100000 ohms.

   Results:

   OK - The resistance is greater than 100000 ohms. Repeat steps 1 to 3 for the other field winding lead (2). If all of the results are OK, the stator is normal. STOP.

   NOT OK - The resistance is NOT greater than 100000 ohms. The field winding lead is shorted to the frame. Replace the field winding. STOP.