TM 1-1500-204-23-4 NOTE In the event the following inspections reveal that the switches are unserviceable, replace    defective    switches    with switches   of   the   same   type   and current rating. (1)    Conduct     a     visual     examination     for physical  damage,  and  check  to  see  that  switches  are securely attached to the mounting panel. (2)  Check  for  loose  or  deformed  electrical connections  or  evidence  of  corrosion  of  the  terminals, terminal lugs or screws. (3) Check for manual operation by actuating toggle lever several times.  This also serves to remove any superficial contamination or foreign deposits on the internal   electrical   contacts.      Return   toggle   lever   to proper position. (4) Test for electrical continuity as measured across the external terminals by means of an ohmmeter.      Electrical   resistance   across   any   set   of closed contacts should not exceed 1 ohm.  Intermittent or   excessive   resistance   normally   indicates   that   the internal   contacts   are   corroded.      In   the   event   a   few additional actuations of the switch does not clear up this condition,  replace  the  switch  with  like  item.    Continuity tests   of   installed   switches   require   that   the   switch   be electrically   isolated   from   other   circuitry   to   preclude measurement  of  low  resistance  parallel  systems.    This can   usually   be   accomplished   by   opening   the   circuit breaker or fuse on the line side of the switches. (5)    Check    switches    that    are    frequently exposed   to   direct   water   spray,   rain   or   heavy   dust concentration.  These switches require timely checks for manual operation, corrosion and continuity. n.  Circuit Breakers.  Inspect circuit breakers using the following procedures: NOTE Replace breakers with breakers of the  same  type  and  current  rating unless otherwise specified, providing the following inspections reveal that the breaker is unserviceable. (1)   Determine   that   the   breaker   case   and mounting means are secure to the mounting panel and there is no evidence of physical damage. (2) Inspect for loose electrical termination or evidence  of  corrosion  of  the  terminals,  terminal  lugs  or screws. (3)   Ensure   positive   manual   operation   by actuating push-pull button or toggle several times.  This operation     also     serves     to     remove     any     superficial contaminants or foreign deposits present on the surface, of  the  internal  electrical  contacts.    Return  actuator  to proper position. (4)   Check   for   evidence   that   breaker   had been  subjected  to  burning  or  overheating  in  the  area adjacent  to  the  manual  actuator.    The  burned  area  is usually   caused   by   electrical   arcing   as   a   result   of   a combination of the presence of excessive moisture and poor dielectric characteristics of the breaker. CAUTION Do not connect ohmmeter to a live circuit. (5) Test for electrical continuity, as measured across the external breaker terminals.  Use a reliable  ohmmeter  capable  of  indicating  an  appropriate dc resistance value for the purpose of determining that the   maximum   overall   electrical   resistance   does   not exceed   1   ohm.      Intermittent   or   excessive   resistance readings   normally   indicate   that   the   internal   breaker contacts  are  corroded.    In  the  event  a  few  additional actuations of the breaker do not clear up this condition, the   breaker   should   be   replaced.      Continuity   tests   of installed breakers require that the breaker be electrically isolated from other circuitry to preclude measurement of low  resistance  parallel  systems.    This  can  usually  be accomplished by opening the switch or switches on the load side of the breaker.  Circuit breakers in live circuits can be checked by performing a voltage check. (6)  Test  and  physically  inspect  associated wiring for short circuit condition to the aircraft structure. Tripped    circuit    breakers    indicate    that    an    abnormal electrical    overload    occurred    and    require    immediate investigation    to    determine    the    cause    for    the    fault. Repetitive  tripping  in  the  same  circuit  will  require  an engineering  investigation  if  the  operating  equipment  or electrical   load   otherwise   functions   properly   and   the breaker replacement does not correct the fault. (7) Check circuit breakers that are frequently  exposed  to  direct  water  spray,  rain,  snow  or heavy   dust   concentrations.      These   breakers   require timely checks for manual operation, corrosion, continuity, evidence of burning or electrical arcing. 3-8