Is it possible to bench-test an alternator?

How do you test an alternator using a multimeter?

Check your alternator by opening the hood of your car and connecting a voltmeter with the car's battery. The red lead should be connected to the positive terminal, and the black lead the negative terminal. After the voltagemeter has read at least 12.2 V, turn on the car and rev it to 2,000 RPM.

What causes an alternator failure? A common reason for alternator failure is bad diodes. The rectifier assembly converts the alternator’s AC output into DC. Leakage can also cause current to drain from the alternator and battery when the vehicle isn't being driven.

It is also important to understand if an alternator can pass a test and be good.

Bench testing an alternator on a stand is the only way to determine if it is working properly. A vehicle equipped with a digital voltagemeter can test the charging output. If the alternator produces normal voltage and current in a bench test, it is not the problem but the vehicle itself.

How can I tell if my voltage regulator or alternator is defective?

A bad voltage regulator can cause dimming, pulsing lights and dead batteries. A bad voltage regulator can also cause electrical equipment to not turn on. The regulator could be cutting off power or allowing too much power through, causing damage to other components.