TM 5-6115-593-12 TO 35C2-3-463-1 (when  it  senses  this  condition)  opens its  normally  closed  contacts,  thereby deenergizing fuel solenoid L1. (4) Coolant  Temperature.    If  the  engine coolant   rises   above   213   +3°F   (100 +0.7°C),  engine  damage  may  occur. Water temperature switch WT1 senses coolant temperature and operates   to   an   open   position   when this temperature becomes too high. (5) Low Fuel Level.  In addition to the fact that engine damage may occur, if the engine   ran   completely   out   of   fuel, trying to restart the engine with a new supply     of     fuel     would     require     an elaborate and time-consuming "bleeding"  procedure.    To  avoid  this, fuel level switch FL1 is used to sense when there is only enough fuel for one more   hour   of   engine   operation   and shuts the engine down by deactivating relay K8 (K8 contacts open the circuit holding fuel solenoid L1 energized). i. Engine  Fault  Indicators.    If  an  engine  fault occurs, the engine will shut down and one of several   indicator   lamps   (mounted   on   the Generator    Control    Panel)    will    light.        In addition to the indicator lamp an annunciator (horn) will sound to alarm crew members not in the immediate vicinity.  To ensure    proper    operation    of    these    faults indicators, a means whereby the lamps and the  annunciator  may  be  tested  is  provided. Since  all  of  these  circuits  act  in  a  similar manner only one will be described. If a high oil temperature condition exists, the normally  open  contacts  of  switch  OT2  will close,   applying   +24-volts   dc   to   energize K28.    Relay  K28  is  held  energized  by  self- latching  contacts  in  parallel  with  OT2.    At this  time  ENG  FAULT  indicator  lamp  DS28 lights    as    24V    DC    is    applied    to    closed contacts  of  S14,  thermal  fuse  FC1,  diode CR30     through     DS28,     CR7,     and     relay contacts K28 to the 24 volt return. Coincident     with     this     action     relay     K28 energizes (through normally closed contacts S13, OT2 and K28) and as a result the horn activates   via   normally   open   contacts   K26 and normally closed contacts K25B. When ANNUNCIATOR TEST switch S13 is set  to  on,  the  horn  is  activated  to  its  test position  through  contacts  8  and  15  of  S13. To  test  indicator  lamp  DS28,  -24V  DC  is applied   through   contacts   7   and   4,   diode CR6,  DS28,  and  back  to  +24V  DC  through contacts 2 and 3 of S13 (the path consisting of CR7 and K28 is disconnected from +24V DC   by   open   contacts   6   and   11   of   S13). Occasionally it may be beneficial to silence the annunciator by toggling ALARM SILENCE   switch   S12   to   the   on   position. With     S12     on,     relay     K25A     and     K25B energize.    The  contacts  of  K25A  hold  the K25A and K25B coil energized when S12 is released and the contacts K25B disconnect the  horn  circuit.  Operating  ANNUNCIATOR RESET switch S14 to on disconnects K25A and K25B from -24V DC and re-enables the horn circuit. j. Engine   Operation.      Once   the   engine   is running    it    is    only    necessary    to    monitor various   operating   parameters   and   to   vary engine     speed     as     required     to     set     the generator output frequency. (1) Engine   Speed.      Controlling   engine speed  is  achieved  by  varying  engine fuel   intake   by   means   of   an   electro hydraulic  governor.    The  operation  of this governor is electrically determined     by     governor     controller A106. Engine speed may be manually adjusted by setting FREQUENCY  ADJUST  switch  S5  to either INCREASE or DECREASE.  S5 controls   two-way   motor   B4   which   is mechanically coupled to potentiometer R102. R102 is electrically   connected   to   A106   and affects its operation. (2) Engine   Monitoring.      Located   on   the Engine Control Panel are four gauges M1   through   M4   which,   respectively, monitor 1-25