What equipment is needed to test the alternator?

A fully charged battery, a 30-volt voltmeter, and suitable test probes are necessary for the test.

What does it mean if the B terminal voltage is more than 15.5V at 1,500 rpm?

The IC regulator (IC-RG) is faulty and should be replaced. A reading of 13 to 15V leads to a further check at idle with the lighting switch ON.

What do the abbreviations A.C.G., IC-RG, and O.K. mean in the flowchart?

A.C.G. means alternator parts except the IC regulator; IC-RG means the IC regulator; O.K. means the IC-alternator is in good condition. 'Light' refers to the charge warning light.

How is the F terminal grounded during the test?

Insert a screwdriver between the ground tab and the rear cover of the alternator, as shown in the illustration (SEL890A).

What voltage across the B and L terminals indicates a faulty alternator?

With the engine idling, more than 0.5V measured between the B terminal (positive lead) and L terminal (negative lead) indicates faulty A.C.G.; less than 0.5V is O.K.

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Nissan Charging System Troubleshooting Flowchart - IC Regulator Alternator EL-24

Charging system trouble-shooting flowchart with IC regulator test steps

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Service manual page with a charging-system troubleshooting flowchart for testing an alternator with an IC regulator.

AI caption February 2006 · Photo 370 of 412

This is page EL-24 of a Nissan service manual covering charging system trouble-shooting for alternators with an IC regulator. It states prerequisites for testing: a fully charged battery, a 30-volt voltmeter, and suitable test probes. The core of the page is a diagnostic flowchart that begins with the ignition switch ON and checks the charge warning light behavior at each step. Depending on whether the light is ON or OFF at idle, at 1,500 rpm with the lighting switch ON, and with connectors (S, L) disconnected or the F terminal grounded, the chart directs the technician to conclusions such as a burned-out bulb (replace and restart procedure), a faulty IC regulator (IC-RG, replace), faulty alternator components other than the regulator (A.C.G.), or a good IC-alternator (O.K.). Key voltage thresholds are given: more/less than 0.5V measured across the B and L terminals at idle, and more than 15.5V versus 13–15V at the B terminal at 1,500 rpm. Footnotes define abbreviations, instruct removal and disassembly of the alternator when 'Faulty A.C.G.' is reached, and describe grounding the F terminal by inserting a screwdriver between the ground tab and rear cover (illustration SEL890A). Terminals B and E are marked on the alternator rear cover.

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Frequently asked questions

What equipment is needed to test the alternator?: A fully charged battery, a 30-volt voltmeter, and suitable test probes are necessary for the test.
What does it mean if the B terminal voltage is more than 15.5V at 1,500 rpm?: The IC regulator (IC-RG) is faulty and should be replaced. A reading of 13 to 15V leads to a further check at idle with the lighting switch ON.
What do the abbreviations A.C.G., IC-RG, and O.K. mean in the flowchart?: A.C.G. means alternator parts except the IC regulator; IC-RG means the IC regulator; O.K. means the IC-alternator is in good condition. 'Light' refers to the charge warning light.
How is the F terminal grounded during the test?: Insert a screwdriver between the ground tab and the rear cover of the alternator, as shown in the illustration (SEL890A).
What voltage across the B and L terminals indicates a faulty alternator?: With the engine idling, more than 0.5V measured between the B terminal (positive lead) and L terminal (negative lead) indicates faulty A.C.G.; less than 0.5V is O.K.