Mitsubishi Alternators

First, when the ignition switch is turned to On, and before the engine starts, current flows through the charging indicator light then to the alternator and ground, causing the charging light to go on.
Once the engine starts, battery voltage is applied to the alternator ``S'' or ``R'' terminal. The battery voltage imposed on this terminal is monitored by the IC voltage regulator, and according to the voltage detected the IC voltage regulator regulates the alternator field coil current, thus controlling the alternator current.
Once the alternator starts alternator starts generating current, a slightly higher voltage than battery voltage is applied to terminal ``L.'' This prevents current from flowing to the charging indicator light and the light goes off.
At alternator terminal ``B,'' a load current proportional to the battery voltage is produced and is sent to any load. The alternator relay is to ensure charging the battery even when the charging indicator light bulb is burnt out.