TM 5-3810-207-20/TO 36C23-3-37-12 CHAPTER 4 CRANE ENGINE MAINTENANCE INSTRUCTIONS Section I.  CRANE ELECTRICAL SYSTEM 69.  Description The  crane-shovel  24-volt  electrical  system  consists of  two  12-volt  batteries  connected  in  series,  a  starter, generator,  generator  regulator,  ignition  coil,  distributor, spark  plugs,  lights,  gages,  and  the  necessary  wiring  to operate  all  components  of  the  electrical  system.    The generator regulator prevents overworking of the generator    and    overcharging    of    the    batteries.        The ignition coil transforms energy into high tension current which  flows  to  the  distributor  and  is  distributed  to  the spark  plugs.    For  proper  removal  and  installation  of  all wiring on the crane, refer to the wiring diagram (fig.  1). 70.  Batteries, Cables, and Battery Box a. Removal. (1) Remove   the   battery   box   cover   (TM   5- 3810-207-10). (2) Remove the batteries, cables, and box in a   numerical   sequence   as   instructed   on figure 6. b. Cleaning, Inspection, and Repair. (1) Clean all parts and inspect for defects. (2) Replace defective parts. c. Test.    Test  the  batteries  with  a  hydrometer.    If the   specific   gravity   reads   below   1.225,   recharge   the batteries.    Test  the  batteries  after  recharging.    A  fully charged  battery  should  read  between  1.280  and  1.300. Replace a battery that will not take or hold a charge. d. Installation. (1) Install    the    battery    box,    batteries,    and cables  in  reverse  numerical  sequence  as instructed on figure 6. (2) Install  the  battery  box  cover  (TM  5-3810- 207-10). 71.  Generator Drive Belt a. Removal.    Remove  the  drive  belt  as  instructed on figure 7. b. Cleaning and Inspection. (1) Clean the drive belt with a cloth dampened    with    an    approved    cleaning solvent. (2) Inspect  the  drive  belt  for  cracks,  breaks, and frayed or stretched condition. Replace defective drive belt. c. Installation.    Install  the  generator  drive  belt  as illustrated on figure 7. d. Adjust the generator drive belt (TM 5-3810-207- 10). 72.  Generator Assembly a. Removal.    Remove  the  generator  assembly  as instructed on figure 7. b. Cleaning and Inspection.  Clean and inspect the generator  and  mounting.    Replace  defective  generator and mounting. c. Installation.    Install  the  generator  assembly  as illustrated on figure 7. d. Test. (1) Hook voltmeter (par.  73). (2) Start  engine  and  slowly  build  up  rpm  to operating    speed.        Observe    voltmeter. The minimum voltage is 27.5 volts. (3) If voltage is not built up to required value, generator is bad; replace generator. e. Brush Replacement. Replace generator brushes as instructed on figure 8. 29