TM   5-3805-258-24-1 E  L  E  C  T  R  I  C  A  L   S  Y  S  T  E M T E S T I N G  A N D  A D J U S T I N G Most of the tests of the electrical system can be done on the engine. The wiring insulation must be in good condition, the wire and cable connections must be clean and tight, and the battery must be fully charged. If the on the engine test shows a defect in a component, remove the component for more testing. ELECTRICAL  SYSTEM an 8 V battery will show 6 V; a 12V battery will show 9 V. Each cell of a battery in good condition must show 1.6 V on either a 6, 8 or 12 V battery. Make  reference  to  Special  Instruction  Form  No. SEHS6891  when  checking  with  the  9S1990  or The service manual TESTING AND ADJUST- ING  ELECTRICAL  COMPONENTS,  Form  No. REG00636  has  complete  specifications  and  proce- dures for the components of the starting circuit and the  charging  circuit. BATTERY T o o l s  N e e d e d : 5 P 3 0 0  E l e c t r i c a l  T e s t e r . 9 S 1 9 9 0      o r      1 P 7 4 0 0      B a t t e r y      C h a r g e r      T e s t e r . 5 P 9 5 7     o r     5 P 3 4 1 4     C o o l a n t     a n d     B a t t e r y     T e s t e r. NOTE: Make reference to Special Instruction Form No. SEHS7006 and to the instructions inside of the cover of the tester, when testing with the 5P300 Electrical 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 charg- ing unit are broken while the charging unit is charg- ing. 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. WARNING Never disconnect any charging unit circuit or battery circuit cable from battery when the charging  unit  is  operated.  A  spark  can  cause  an explosion  from  the  flammable  vapor  mixture  of hydrogen and oxygen that is released from the electrolyte through the battery outlets. Injury to personnel can be the result. Load test a battery that does not hold a charge when in use. To do this, put a resistance, across the main connections (terminals) of the battery. For a 6, 8 or 12 V battery, use a test load of three times the ampere/hour rating (the maximum test load on any battery is 500 amperes). Let the test load remove the charge (discharge) of the battery for 15 seconds and with the test load still applied test the battery vol- tage. A 6 V battery in good condition will show 4.5 V; 1P7400  Battery  Charger  Tester. 9S1990    BATTERY    CHARGER    TESTER CHARGING   SYSTEM T o o l s      N e e d e d :      5 P 3 0 0      E l e c t r i c a l      T e s t e r . NOTE: Make reference to Special Instruction Form No. SEHS7006 and to the instructions inside of the cover of the tester, when testing with the 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 constantly in a low condition of charge or a large amount of water is needed (more than one ounce of water per cell per week or per every 50 service hours). Make a test of the charging unit and voltage reg- ulator on the engine, when possible, use wiring and components that are a permanent part of the system. Off the engine (bench) testing will give a test of the charging  unit  and  voltage  regulator  operation.  This testing will give an indication of needed repair. After tests are made, again make a test to give proof that the  units  are  repaired  to  their  original  operating condition. Before starting the on engine testing, the charging system and battery must be checked is given in^-the Steps   below. 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. 4-40