HARNESS AS 1341322 - Caterpillar

Features of the Built-in Alternator(1) For better voltage buildup especially at idle speeds, the alternator is provided with the R terminal independent from the L terminal (charge lamp circuit) as the initial excitation circuit.(2) The three diodes (diode trio) built into the alternator apply the field current directly to the field coil, eliminating voltage drop caused by the starter switch and wiring.(3) The P terminal is for detecting the safety relay frequency. OperationWhen the starter switch is turned ON, base current flows from the battery to power transistor to turn it ON, allowing the current to flow through the field coil to turn on the charge lamp. As the engine starts with the alternator generating power, the base current is supplied by the alternator itself.The field current also flows from the diode trio to energize the rotor.At the time the charge lamp goes off, since the output voltage from the B terminal becomes the same as that from the L terminal. As the voltage developed by the alternator builds up, the zener diode Dz conducts providing base current for the transistor Trl to turn it ON.As a result, the base current of the power transistor is shorted to Trl, which turns OFF the power transistor. This means that there is no field current flow, dropping the voltage generated by the alternator.When the zener diode Dz is shut off with a voltage drop, the base current flows to the power transistor to turn it ON. As a result, the field current again starts flowing, increasing the generated voltage.These IC regulator operations repeat to regulate the alternator voltage.1-3 Vacuum Pump
The vacuum pump is of a rotary type with movable vanes. The rotor with three movable vanes turns in the housing of a cylindrical shape. The housing is mounted on the rear bracket of the alternator with the rotor spline-coupled into the alternator shaft.The rotor and housing are eccentric. The air drawn in through the suction port is gradually compressed and discharged from the deliver port. Oil is also drawn in through the oil filler port to provide sealing, lubricating, and cooling functions for the housing, and discharged from the deliver port with the compressed air to the oil pan. The check valve prevents the engine oil and compressed air from flowing back to the vacuum tank when the engine is stationary. 1-4 Safety Relay
The alternator rpm is detected and when it exceeds the reference level, the safety relay prevents the starter from operating even if its switch is accidentally turned on during engine revolution.Operation (1) When the starter switch is set to ON, current flow from the starter relay to terminal "S" and to terminal "E" of the safety relay, closing contact P1. The charge lamp also illuminates if provided.(2) As the starter runs and the engine starts running, pulses of frequency 1/10th of the alternator speed appear at terminal "P" of the alternator. The charge lamp goes out.(3) When the pulse frequency at terminal "P" exceeds the specified value,