N3 Series Brushless Alternators Caterpillar

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Personal injury or death can result from a spark. An incompletely discharged capacitor can cause a spark. Discharge the suppression capacitor before testing. This prevents the igniting of flammable fluid from sparks caused by capacitor discharge.

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

Illustration 1	g00867657
(1) Lead for the suppression capacitor (B-) "B-" terminal (D+) "D+" terminal

1. Remove the rear cover.

2. Disconnect the lead for the suppression capacitor (1) from the "D+" terminal on the back of the alternator.

3. Touch the wire assembly (1) to one of the capacitor mounting screws in order to discharge the capacitor.

4. Connect one lead of the multimeter to the lead of the suppression capacitor (1). Connect the other lead of the multimeter to the "B-" terminal. This is shown in illustration 1.

5. Measure the resistance between the terminals.

   Expected Result: The resistance is low for a short period of time. The resistance stabilizes above 200000 ohms.

   Results:

   OK - The resistance stabilizes above 200000 ohms. The capacitor is normal. Repeat step 3. STOP.

   NOT OK - The resistance does NOT stabilize above 200000 ohms. The capacitor has failed. Replace the capacitor. STOP.