Alternator & Regulator: Description

Mitsubishi conventional 3-phase, self-rectifying alternator contains 8 diodes (4 positive and 4 negative) that rectify current. See Figure.

The internal circuitry of a Mitsubishi IC regulator consists of 3 circuits. See Figure. Circuit No. 1 functions when ignition is first turned on and engine is off. With ignition switch in ON position, the charge indicator light comes on to show a current flow of less than .5 amps flowing through field coil. If indicator light is not on, the fault may be one of the following: burned out indicator bulb, break in field coil wiring defective IC regulator, or worn brushes.

Circuit No. 2 functions when alternator turns and generates voltage. The charge indicator light goes out because voltage at both ends of light bulb is now equal. Field current is now supplied from diodes. When voltage at connection "a" (between resistors Rv and R1) is low voltage, no voltage flows into Zener diode Dz, keeping transistor Tr1 turned off.

Voltage flows into power transistor, (large circle in wiring diagram) turning it on and allowing field current to flow through it, creating voltage. In this condition, when current voltage exceeds battery voltage at terminal "B" of IC regulator, excess current voltage flows to charge battery.

Circuit No. 3 functions when alternator creates too much voltage at terminal "L" of IC regulator. This increases voltage at connection "a" (between resistors Rv and R1). When increased "a" voltage exceeds rated value of Zener diode Dz, current flows through diode Dz and turns on transistor Tr1. This condition turns off power transistor and "regulates" voltage output to preset parameters (14.0-15.0 volts). IC regulator continually repeats operation of circuits No. 2 and 3 to regulate voltage.