TM 1-1510-223-10 The plumbing from the compressor is routed through the right inboard wing leading edge to the fuselage and then forward  to  the  condenser  coil,  receiver-dryer,  expansion valve,  bypass  valve,  and  forward  evaporator,  which  are located  in  the  nose  of  the  aircraft.    A  7.5-ampere  circuit breaker,  placarded  AIR  COND  CONTR,  located  on  the overhead  circuit  breaker  panel  (fig.    2-7),  protects  the compressor clutch circuit. (1)   Forward evaporator.   The forward evaporator and blower supplies airflow for the cockpit, forward ceiling outlets, and forward floor outlets.  The forward evaporator blower has a high speed, which can be selected by setting the    VENT    BLOWER    FWD    switch,    located    on    the overhead control panel (fig.  2-13), to the HIGH position. The forward vent blower is protected by a circuit breaker located   on   the   DC   power   distribution   panel,   located beneath the aisleway. (2)   Aft    evaporator.       The    aft    evaporator    and blower are located in the fuselage center aisle equipment bay, aft of the rear spar.  Environmental air is circulated through   the   evaporator   in   either   manual   or   automatic control  modes.    The  rear  evaporator  supplies  airflow  for the    aft    ceiling    outlets,    rear    floor    outlets,    and    toilet compartment.  The rear evaporator blower is protected by a   circuit   breaker   located   on   the   DC   power   distribution panel, located beneath the aisleway. (3)   High  and  low  pressure  limit  switches.    High and  low  pressure  limit  switches  are  provided  to  prevent compressor  operation  beyond  operational  limits.    When the     low     or     high     pressure     switches     are     activated, compressor operation will be terminated. When compressor operation has been terminated by limit switch activation,   the   system   should   be   thoroughly   checked before returning it to service. (4)   Thermal   sense   switch.       A   thermal   sense switch is installed on the forward evaporator.  This sense switch actuates a hot gas bypass valve which bypasses a portion   of   the   refrigerant   from   the   forward   evaporator, thereby preventing icing of the evaporator. (5)   Condenser    blower.       A    vane-axial    blower draws  air  through  the  condenser  when  aircraft  is  on  the ground.    The  blower  is  protected  by  a  50-ampere  circuit breaker  located  beneath  the  aisleway.    When  the  cabin temperature mode selector switch is set to the AC COLD OPN   position   during   ground   operation,   the   condenser blower   will   be   off   initially,   and   will   remain   off   until compressor    discharge    pressure    equals    the    pressure setting  of  the  blower  control  high  pressure  switch.    The blower   will   remain   in   operation   until   system   pressure drops to equal the setting of the blower control low pres- sure switch. (6)   Air  conditioning  cold  operation  bypass  valve. Selecting  the  AC  COLD  OPN  mode  on  the  CABIN  AIR MODE SELECT switch (fig.  2-13), permits the operation of the air conditioning system by overriding the refrigerant low   pressure   switch.      This   allows   the   air   conditioning system   to   operate   in   the   manual   mode.      Starting   the compressor    in    this    optional    mode    at    low    ambient temperature   will   decrease   the   operational   life   of   the compressor  by  five  hours  each  time  the  air  conditioning system is started below 10°C using this mode (AC COLD OPN).  If the air conditioning system has been operating in the normal mode during flight, and decreasing ambient temperatures make it necessary to switch to the AC cold operation mode, there will be no degradation in the mean time between failure for the compressor. (7)   Air conditioner cold operation.  Air conditioner cold    operation    mode    is    provided    to    allow    the    air conditioner to operate in the event of a hot cabin and an outside air temperature of less than 10°C.  At an OAT of less  than  10°C,  a  green  advisory  annunciator  placarded AC COLD OPN, located on the caution/advisory annunciator  panel  will  illuminate.    This  advises  the  crew that if air conditioning is required, the CABIN AIR MODE SELECT  switch  must  be  in  the  AC  COLD  OPN  position. This    causes    the    air    conditioner    compressor    to    run continuously and the temperature controller to operate the bypass valve. b. Normal Operation. (1)   Automatic cooling mode. 1. BLEED  AIR valve switches - ON, LEFT and RIGHT. 2. CABIN AIR MODE SELECT switch - AUTO. 3. CABIN AIR TEMP CONTROL rheostat - As required. 4. CABIN, PILOT, COPILOT, and DEFROST AIR knobs - As required. (2)   Manual cooling mode. 1. BLEED AIR valve switches - ON, LEFT and RIGHT. NOTE For  maximum  cooling  on  the  ground,  set  the BLEED   AIR   valve   switches   to   the   PNEU ONLY position. 2. CABIN AIR MODE SELECT switch - MAN COOL. 2-61