Relay Adjustment And Repair

a. Description. The relay is provided with an additional contact for the normally open position to control the signal light in the instrument panel. When the generator voltage exceeds the battery voltage (between 6.3 and 6.8 volts) the relay closes the battery-generator circuit. At this time, the upper contact points break and the panel green indicator light goes off, indicating that the generator is charging the battery. This occurs at approximately 20 miles per hour in high gear.

1ยป. Adjustment (fig. 79). The relay contact points must be correctly adjusted and the armature must have correct spacing above the magnet core for sensitive and correct cut-in and cut-out operation.

(1) Armature and Core Air Gap. The space (air gap) between the armature and magnet core end is 0.015 inch when the two upper points are in contact. Bend upper contact point support and adjust armature to obtain this gap.

(2) Main Contact Point Gap. After the armature and magnet core end air gap have been adjusted, gage the main contact point gap. It should be 0.020 inch and can be obtained by bending the lower point support up or down as may be necessary.

(3) Signal Point Gap. Press the armature down until the lower main points are in contact and gage the upper contact point gap. It should be 0.020 inch and can be obtained by bending the upper point support up or down as necessary.

(4) Adjusting Armature Spring Tension. The relay main lower points should close at 6.3 to 6.8 volts (connect voltmeter to relay terminal marked "GEN" and to the relay base), and can be adjusted by decreasing or increasing the armature spring tension. Increasing the armature spring tension increases the closing voltage, while decreasing the spring tension reduces the closing voltage. The armature spring tension is altered by bending the spring stop, mounted on top of the magnet, up or down.

e. Repair. The relay should not be disassembled for attempted repair. A relay worn or damaged beyond adjustment service, must be replaced.


a. This switch is fitted to late WLA models. For diagram of earlier system, refer to TM 9-879. Although this magentic switch is put into action only by use of the blackout headlight, it actually controls the generator shunt field coil when this headlight is in use; therefore, it should be considered a part of the generating system. Refer to wiring diagram, figure 65. The generator field magnetic switch is a sealed unit, and if found faulty and/or damaged it must be replaced.


a. Table of Fits and Tolerances.

(1) Armature Clearance Between Pole Shoes. 0.007 inch clearance between armature core and each pole shoe.

(2) Brush Length. New brushes are approximately 13/16 inch long on the longest side. Replace when longest side is inch or less in length.

(3) Armature Shaft Bearing Diameter, Commutator End. Shaft diameter for the small ball bearing is 0.472 inch.

(4) Armature Shaft Bearing Diameter, Drive Gear End. Shaft diameter for the large ball bearing is 0.5912 inch.

(5) Bearing Fits. Ball bearing inner and outer races are a light press fit on the armature shaft and in the housings respectively.

Section I

DIY Battery Repair

DIY Battery Repair

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