TM 1-1500-204-23-4 o.    Kapton  Wiring.    Kapton  wire  MIL-W-81381  is general purpose wire for use in high voltage applications.      The   insulation   is   tape   of   polyimide   or polyimide-fluorocarbon films.  The conductors are silver or nickel plated copper, or a high-strength copper alloy. At  present  Kapton  wiring  is  being  phased  out  on  new aircraft  and  is  restricted  to  ballistically  hardened  areas. The   preferred   wire   is   MIL-W-22759   which   cannot   be mixed in the same wire bundle as Kapton wire.  Refer to TM     55-1500-323-24     for     inspection,     stripping,     and installation   of   connectors   on   Kapton   wiring.      Kapton insulated wire should be inspected whenever maintenance is performed.  Slight flaking of top coat is acceptable, however this is considered as a first stage of deterioration. When flaking is observed, dose inspection   shall   be   performed   at   regular   intervals   to determine   if   further   deterioration   occurs.      Excessive flaking or other damage (cuts, chaffing, etc) to insulation requires that the wire be replaced. 3-2.  Troubleshooting .  Troubleshoot electrical circuits and  components  when  malfunctions  cannot  be  readily located.  Use procedures outlined below. CAUTION Omit  operational  check  in  cases where it is evident that an operational  check  could  result  in damage to the aircraft. a.    Operational  Check.    Perform  an  operational check  of  the  system  involved  to  determine  when  it  is functioning   in   accordance   with   the   applicable   aircraft maintenance    manual.        When    a    malfunction    exists, perform the following procedures: (1)   Obtain    a    wiring    diagram    of    system involved.        Be    sure    wiring    diagram    is    current    and applicable to particular model aircraft. (2) Review operating principles and performance requirements of the system. (3)    Recall    similar    situations    and    check Equipment Improvement Recommendation (EIR) file. (4)  Examine  aircraft  maintenance  forms  to see  what  maintenance  has  been  performed  on  system or general area of system or components. (5)  Decide  on  all  possible  component  and wiring    malfunctions    which    could    cause    system    to perform    as    it    does.        A    typical    electrical    system schematic is shown in figure 2-4. (6) Of all possible faults or troubles found in step (5), decide which troubles are most probable cause of     malfunctions     and     proceed     to     test     circuits     or components with test equipment. NOTE The applicable aircraft maintenance manual contains troubleshooting  electrical  circuits and components. (7) Upon location of defective component or wiring, accomplish repairs or replacements as necessary. b.   Precautions.  Use of test equipment designed primarily  for  high  potential  voltage  testing  on  aircraft electrical  cabling  can  be  extremely  hazardous  in  those areas   where   fuels,   explosive   vapors,   or   fumes   are present in the aircraft.  The term high potential voltage testing  as  used  herein  is  described  as  that  condition  of applying a voltage of sufficient magnitude and approaching  maximum  insulation  breakdown  limits  as specified to determine leakage resistance between wire insulation,   conductors,   conductor   pairs,   or   groups   of conductors   individually   insulated   within   an   insulated cable    jacket.        High    potential    voltage    or    insulation breakdown    testing    of    aircraft    electrical    wiring    and cabling   will   be   conducted   as   a   last   resort   after   all previous methods of detecting faulty cabling have been accomplished.  These methods will consist of continuity, visual   inspection,   common   voltmeter   and   ohmmeter checks,  and  other  methods  not  involving  high  potential voltage tests.  The following procedures will apply where tests,   employing   high   potential   testers,   are   made   to check   aircraft   electrical   cabling   and   wiring   involving those   areas   where   fuels,   fumes,   or   explosive   vapors may possibly be present: (1)    It    will    be    the    responsibility    of    all personnel using high potential voltage test apparatus to trace the physical location of the circuit being tested and determine   if   explosive   vapors,   fuels   or   fumes,   are present in any areas of this circuit. (2) When explosive vapors, fuels, or fumes are  determined  to  be  present  and  adequate  ventilation or   air   circulation   is   not   provided,   the   following   two paragraphs will apply: (a)    If     fumes     or     vapors     can     be removed  by  isolating  fuel  from  the  areas  involved  by means  of  shutoff  or  bypass  valves,  only  that  portion  of the  fuel  system  which  is  isolated  must  be  drained  and purged. 3-9