TM 10-3930-653-14&P The  clearance  should  be  held  within  0.5  to  2.0  mm (0.020 to 0.079 in). If necessary, adjust it by changing or adding    adjusting    washer(s).    Adjusting    washers    are available in two different sizes, 0.5 mm (0.020 in) and 0.8 mm (0.031 in). Fig.  4-170.  Measuring Gap "l”” 4-7-4.  CHARGING CIRCUIT The charging circuit consists of the battery, alternator,   regulator   and   necessary   wiring   to   connect these  parts.  The  purpose  of  this  system  Is  to  convert mechanical energy from the engine into electrical energy which  is  used  to  operate  all  electrically  operated  units and to keep the battery fully charged. When the ignition switch is set to "ON", current flows from  the  battery  to  ground  through  the  ignition  switch, voltage  regulator  IG  terminal,    primary    side    contact point  "P1," movable contact point "P2", voltage regulator "F"    terminal,    alternator    "F"    terminal.    field    coil    and alternator "E" terminal. as shown in Fig.  7-22 by full line arrow  marks.  Then  the  rotor  in  the  alternator  is  excited. On   the   other   hand,   current   flows   from   the   battery   to ground through the ignition switch, warning lamp, voltage regulator   "L"   terminal,   lamp   side   contact   point   "P4," movable  contact  point  "PS,"  and  voltage  regulator  "E" terminal, as shown by dotted line arrow marks. Then. the warning lamp comes on. When  the  alternator  begins  to  operate,  three  phase alternating   current   is   induced   in   the   stator   cold.   This alternating    current    is    rectified    by    the    positive    and negative silicon diodes. The rectified direct current output reaches the "A" and "E" terminals of the alternator. On the other hand, the neutral point voltage reaches "N" and "E" terminals (nearly a half of the output voltage), and current flows from the voltage regulator ’N" terminal to   "E"   terminal   or   ground   through   the   coil   "VC1"   as shown in Fig. 7-23 by the dotted line arrow marks. Then, the  movable  contact  point  "P5"  comes  into  contact  with the voltage sinding side contact point “P6".  This  action causes  the  warning  lamp  to  turn  off  and  complete  the voltage  winding  circuit,  as  shown  by  the  full  line  arrow marks. When   the   alternator   speed   is   increased   or   the voltage  starts  to  rise  excessively,  the  movable  contact point  "P2"  is  separated  from  the  primary  side  contact "P1" by the magnetic force of the coil "VC2." Therefore, the  resistor  "R1"  is  applied  into  the  rotor  circuit  and output  voltage  is  decreased  As  the  output  voltage  is decreased. the moveable contact point "P2" and primary side contact "P1" comes into contact once again, and the alternator voltage increases. Thus, the rapid vibration of the  movable  contact  point  "P2",  maintains  an  alternator constant output voltage. When the alternator speed is further increased or the voltage  starts  to  rise  excessively,  the  movable  contact point   "P2"   comes   into   contact   with   secondary   side contact point "P3". Then, the rotor current is shut off and alternator output voltage is decreased immediately. This action  causes  to  separate  movable  contact  "P2"  from secondary contact "P3". Thus, the rapid vibration of the movable  contact  point  "P2"  or  breaking  and  completing the  rotor  circuit  maintains  an  alternator  constant  output voltage. 4-101