To  test  the  switch,  touch  the  test  light  to  the  switch output  wire  connection  while  moving  the  shift  lever. The light should glow as the shift lever is slid into park or  neutral.  The  light  should  not  work  in  any  other position. If the light is not working properly, check the mechanism that operates the switch. If the problem is in the switch, replace it. Starter Current Draw Test STARTING  CIRCUIT  MAINTENANCE The  condition  of  the  starting  motor  should  be carefully  checked  at  each  PM  service.  This  permits  you to take appropriate action, where needed, so equipment failures caused by a faulty starter can be reduced, if not eliminated. The starter current draw test measures the amount of amperage used by the starting circuit. It quickly tells you about the condition of the starting motor and other circuit  components.  If  the  current  draw  is  lower  or higher  than  the  manufacturer’s  specifications,  there  is  a problem in the circuit. A  visual  inspection  for  clean,  tight  electrical connections  and  secure  mounting  at  the  flywheel housing is the extent of the maintenance check. Then operate  the  starter  and  observe  the  speed  of  rotation and the steadiness of operation. To prevent the starter from overheating, do NOT operate the starter for more than 30 seconds. To perform a starter current draw test, you may use either  a  voltmeter  or  inductive  ammeter  or  a  battery load tester. These meters are connected to the battery to measure  battery  voltage  and  current  flow  out  of  the battery.  For  setup  procedures,  use  the  manufacturer’s manual for the type of meter you intend to use. If the starter is not operating properly, remove the starter, disassemble it, and check the commutator and brushes. If the commutator is dirty, it may be cleaned with  a  piece  of  No.  00  sandpaper.  However,  if  the commutator is rough, pitted, or out-of-round or if the insulation  between  the  commutator  bars  is  high,  it must be reconditioned using an armature lathe. To  keep  a  gasoline  engine  from  starting  during testing, disconnect the coil supply wire or ground the coil  wire.  With  a  diesel  engine,  disable  the  fuel injection system or unhook the fuel shutoff solenoid. Check the manufacturer’s service manual for details. With the engine ready for testing, crank the engine and  note  the  voltage  and  current  readings.  Check  the manufacturer’s service manual. If they are not within specifications,   there   is   something   wrong   with   the starting circuit. Brushes  should  be  at  least  half  of  their  original size. If not, replace them. The brushes should have free movement in the brush holders and make good, clean contact with the commutator. Once the starter is checked and repaired as needed, it should be reassembled, making sure that the starter brushes are seated. Align the housings and install the bolts securely. Install the starter in the opening in the flywheel housing and tighten the attaching bolts to the specified  torque.  Connect  the  cable  and  wire  lead firmly to clean terminals. STARTING  MOTOR  CIRCUIT  TESTS There  are  many  ways  of  testing  a  starting  motor circuit to determine its operating condition. The most common tests are as follows: The starter current draw test is used to measure the  amount  of  amperage  used  by  the  starting circuit. 2-30 The starter circuit voltage drop tests (insulated circuit  resistance  test  and  starter  ground  test)  are used  to  locate  parts  with  higher  than  normal resistance quickly. WARNING Do NOT crank the engine for more than 30 seconds  or  starter  damage  can  result.  If  the starter  is  cranked  too  long,  it  will  overheat. Allow  the  starter  to  cool  for  a  few  minutes  if more cranking time is needed. Starting Circuit Voltage Drop Tests A   voltage   drop   test   will   quickly   locate   a component  with  higher  than  normal  resistance.  This test  provides  an  easy  way  of  checking  circuit condition. You do NOT have to disconnect any wires and  components  to  check  for  voltage  drops.  The  two types  of  voltage  drop  tests  are  the  insulated  circuit resistance test and the starter ground circuit test. INSULATED   CIRCUIT   RESISTANCE TEST.—The  insulated  circuit  resistance  test  checks ail  components  between  the  positive  terminal  of  the battery  and  the  starting  motor  for  excess  resistance.