TM 10-3930-671-24 1. Connect  a  voltmeter  from  the  motor  terminal  to the motor frame. 2. Connect  the  motor  and  an  ammeter  in  series with a fully-charged  12-volt  battery  and  a  switch in  the  OPEN  position  from  the  solenoid  battery terminal to the solenoid switch (R) terminal. 3. Hold the RPM indicator against the exposed end of the armature shaft. 4. Close the switch and compare the rpm, current, and voltage readings with the specifications. 5. Be sure that the  switch  is  OPEN  before  making any disconnections. No-Load Test Diagnosis 1. Rated  current  draw  and  speed  indicates  normal condition of the cranking motor. 2. Low free speed and high current draw indicates: a)    Too    much    friction    -    tight,    dirty,    or    worn bearings,   bent   armature   shaft,   or   loose   pole shoes allowing armature to drag. b) Shorted   armature.      This   can   be   further checked on a growler after disassembly. c) Grounded    armature    or    fields.        Check further after disassembly. 3. Failure     to     operate     with     high     current     draw indicates:    a)  A  direct  ground  in  the  terminal  or fields. b) "Frozen"  bearings  (this  should  have  been determined   by   turning   the   armature   by hand). 4. Failure to operate with no current draw indicates: a) Open field circuit.  This can be checked after disassembly  by  inspecting  internal  connections and tracing circuit with a test lamp. b) Open armature coils. Inspect the commutator   for   badly   burned   bars   after disassembly. c) Broken brush springs, worn brushes, high insulation  between  the  commutator  bars, or other causes which would prevent good contact between the brushes and commutator. 5. Low    no-load    speed     and     low     current     draw indicates   high   internal   resistance   due   to   poor connections,   defective   leads,   dirty   commutator and causes listed under Number 4. 6. High free speed and high current draw indicates shorted  fields.    If  shorted  fields  are  suspected, replace   the   field   coil   assembly   and   check   for improved performance. Starter Disassembly If the starter motor does not perform in accordance with the listed specifications, it may need to be disassembled for further testing of the components. Normally, the starter motor should be disassembled only so far as is necessary to  repair  or  replace  the  defective parts. Refer to Starter Repair (Para 5-20). F-310