Fig. 7. Cranking Circuit Test

TM-5-3820-256-24-4 Drilling System Well Rotary Truck Mounted Air Transportable 600 Feet Capacity Model LP-12 NSN 3820-01-246-4276 Manual
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ENGINE DIVISION SERVICE MANUAL ELECTRICAL Fig. 7. Cranking Circuit Test 1. Voltmeter Values of maximum voltage drops for a standard 12- volt cranking circuit are as follows: Volt Cable Under Three (3) Feet .1 Cable Over Three (3) to Six (6) Feet .2 Mechanical Switch .1 Solenoid Switch .2 Magnetic Switch .3 Each Connection .0 Add these values together. For ex-ample, you have a total of .5 volt and you have less than .5 volt drop, continue to grounded side test. However, if you have more than .5 volt drop, you have an excessive voltage drop. This must be located by moving test lead from starting motor and working toward the battery. Crank engine and each move. When a noticeable decrease in the voltage reading is obtained, the trouble will be located between that point and the preceding point checked. Items which could be at fault can either be a damaged cable or poor connection, an undersized wire or possibly a bad solenoid (contact within the solenoid). Repair the fault. Grounded Size: High resistance in ground circuit of starting motor system will result in hard starting and may affect the charging circuit as well. Connect voltmeter leads to ground on starting motor and to ground post of battery. The allowable voltage drop of .2 volt is permissible. If more than .2 volt is obtained, a poor ground is pre-sent, such as a loose starting motor mounting bolt, bad battery ground connector or ground connection to engine or frame, depending upon the battery installation. The excessive voltage drop is located in much the same manner as in the preceding test working toward the battery. CGES-230 - Page 8 PRINTED IN UNITED STATES OF AMERICA

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