1942 - 1947 Chevrolet Shop Manual



	12-10

	The purpose of the series winding on the voltage regulator is to speed up the vibration of the regulator armature. It will be noted in Fig. 19, that when the regulator points open, the field current passing over the series winding is reduced to zero, resulting in an instant reduction in its magnetic strength, allowing the regulator points to close more rapidly. This, of course, results in holding the generator voltage nearer a constant value. CURRENT REGULATOR When the battery is low and lighting and accessory loads are turned on, the generator voltage may not be forced up high enough to operate the voltage regulator. In this case the current regulator comes into operation. It will be noted by referring to Fig. 16 that all the current for lights, accessories and charging the battery passes through the series winding of the current regulator, also that any change in the current output of the generator makes the same change in the current value passing through the series winding of the regulator. Such being the case, the magnetic strength of the current regulator series winding varies directly as the current output of the generator. As the generator output increases to a predetermined value (34 to 36 amperes fixed by the regulator setting) the magnetic pull on the regulator armature increases until the armature is attracted toward the core, against the spring tension, opening the regulator points. The field circuit must now pass through the upper resistance unit and across the voltage regulator points to ground, and also through the lower resistance unit to ground in order to complete the	circuit. These two resistance units are connected in parallel at this time, Fig. 20. This adds resistance to the shunt field circuit, thereby reducing the current value passing through the field. This, of course, results in a drop in generator voltage and output. This reduction in current value passing through the series winding of the current regulator reduces its magnetic strength, allowing the spring tension to immediately close the regulator points, eliminating the resistance from the field circuit, thus allowing the generator voltage and output to build up again. This cycle of operation occurs many times per second, resulting in holding the maximum amperage output of the generator at a practically constant value. QUICK CHECKS TO DETERMINE IF UNITS ARE OPERATING PROPERLY The following checks must be made to determine whether or not the units are operating normally. If not, the checks will indicate whether the generator or regulator is at fault so that proper corrective steps may be taken: 1. A FULLY CHARGED BATTERY AND A LOW CHARGING RATE indicates normal voltage regulator operation. To check the current regulator remove the battery wire from the battery (BAT) terminal of the regulator. Connect the positive lead of an ammeter to the battery terminal of the regulator and the negative lead to the battery wire. With the ignition switch in the "off" position, step on the starting switch and crank the engine for about fifteen seconds. Then start the engine and, with it running at medium speed, turn on lights, radio and other electrical accessories and note quickly the generator output, which should be the value for which the current regulator is set. Now turn off the lights, radio and other accessories and allow the engine to continue running. As soon as the generator has replaced in the battery the current used in cranking, the voltage regulator, if operating properly, will taper the output down to a few amperes. 2. A FULLY CHARGED BATTERY AND A HIGH CHARGING RATE. (a) Disconnect the field wire from the field (F) terminal of the regulator. This opens the generator field circuit and the output should immediately drop off. If it does not, the generator field circuit is grounded either inside the generator or in the wiring harness. If the output drops off to "Zero" with the field lead disconnected, the trouble has been isolated in the regulator. Reconnect

	Fig. 20-Field Circuit with Current Regulator Points Open