TM 5-3825-226-24 ELECTRICAL SYSTEM Most of the testing of the electrical system can be done on  the  engine.    The  wiring  insulation  must  be  in  good condition, the wire and cable connections clean and tight and the battery fully charged. If on the engine test shows a  defect  in  a  component,  remove  the  component  for more testing. BATTERY Tools Needed: 5P300 Electrical Tester. 9S1990 or 1P7400 Battery Charger Tester. 5P957 or 5P3414 Coolant and Battery Tester. The  battery  circuit  is  an  electrical  load  on  the  charging unit.    The  load  is  variable  because  of  the  condition  of the charge in the battery.  Damage to the charging unit will    result,    if    the    connections,    (either    positive    or negative)   between   the   battery   and   charging   unit   are broken   while   the   charging   unit   is   charging.      This   is because the battery load is lost and there is an increase in charging voltage. High voltage will damage, not only the charging unit but also the regulator and other electrical components. 9S1990 BATTERY CHARGER TESTER CAUTION Never  disconnect  any  charging  unit circuit  or  battery  circuit  cable  from battery   when   the   charging   unit   is charging. Load test a battery that does not hold a charge when in use.    To  do  this,  put  a  resistance,  across  the  battery main connections (terminals).  For a 6 volt battery, put a resistance  of  two  times  the  ampere/  hour  rating  of  the battery.  For a 12 volt battery, put a resistance of three times    the    ampere/    hour    rating.    Let    the    resistance remove    the    charge    (discharge    the    battery)    for    15 seconds.  Immediately test the battery voltage.  A 6 volt battery  in  good  condition  will  test  4.5  volts;  a  12  volt battery in good condition will test 9 volts. CHARGING SYSTEM Tools Needed: 5P300 Electrical Tester. The  condition  of  charge  in  the  battery  at  each  regular inspection will show if the charging system is operating correctly.  An adjustment is necessary when the battery is always in a low condition of charge or a large amount of  water  is  needed  (one  ounce  per  cell  per  week  or every 50 service hours). Test  the  charging  units  and  voltage  regulators  on  the engine,   when   possible,   using   wiring   and   components that are a permanent part of the system. Off the engine (bench)   testing   will   give   an   operational   test   of   the charging  unit  and  voltage  regulator.    This  testing  will give  an  indication  of  needed  repair.    Final  testing  will give  proof  that  the  units  are  repaired  to  their  original operating condition. Before   starting   on   the   engine   testing,   the   charging system and battery must be checked.  See the following Steps. 1. Battery  must  be  at  least  75%  (1.240  Sp.    Gr.) full   charged   and   held   tightly   in   place.      The battery  holder  must  not  put  too  much  stress  on the battery. 2. Cables  between  the  battery,  starter  and  engine ground  must  be  the  correct  size.    Wires  and cables must be free of corrosion and have cable support   clamps   to   prevent   stress   on   battery connections (terminals). 3. Leads, junctions, switches and panel instruments   that   have   direct   relation   to   the charging circuit must give proper circuit control. 4. Inspect  the  drive  components  for  the  charging unit  to  be  sure  they  are  free  of  grease  and  oil and  are  able  to  drive  the  load  of  the  charging unit. Alternator Regulator (Delco-Remy) The   voltage   adjustment   screw   for   the   alternator   is located under the end plate. To    adjust    the    voltage    setting,    use    the    following procedure: 2-76