TM 10-3930-664-10 KEY CONTROL OR INDICATOR FUNCTION 3 Parking Brake Switch In the ON position, applies the parking brake. CAUTION 4 Differential Lock Switch In the ON position, differential lock mechanism in front axle is engaged. 5 Ignition Switch Three position rotary switch controls the flow of current from the batteries to all  of  the  electrical  system  except  lighting.    In  the  OFF  position  the  switch disconnects  the  flow  of  current  between  the  batteries  and  all  controls  and indicators  except  lighting.    Moving  the  switch  to  OFF  deactivates  the  fuel solenoid on the fuel injection pump stopping the flow of fuel from the pump to the injectors and causing the engine to stop.  In the ON position, all controls and  indicators  are  operable.    In  the  START  position,  the  engine  starting motor is engaged.  Engine will not start unless travel and range select lever is in   neutral.      After   engine   starts,   switch   cannot   be   moved   to   the   START position without first being moved to OFF position. Engage differential lock on front axle only when necessary to ensure power is transferred to one wheel if the opposite  wheel  loses  traction  or  is  off  the  ground.    The  differential  lock  should  be  engaged  only  while operating in first gear (F1 or R1) and while driving forward or rearward in a straight line.  Making turns with the differential lock engaged will damage the front axle assembly. 2-2