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TM 5-4120-270-15 (3)    If    valve    fails    to    click    closed,    stop    air conditioner  and  test  valve  according   to   instructions   in paragraph 618. c.  Removal and Disassembly.  Discharge refrigerant system (para 6-28).  Refer to figure 58 and  remove  and disassemble the  liquid line solenoid valve. Caution: Do not remove tubing from valve to avoid heat distortion of integral parts. d.        Reassembly    and    Installation.        Replace    any defective parts.  Reassemble valve and install in reverse order   of   removal   as   illustrated   on   figure   5-8.      Test, evacuate  and  recharge  the  refrigerant  system  (para  6- 28, 29, 30). 6-20.  Back Pressure Regulating Valve a.  General.  The back pressure regulating valve (fig. 5-9),  regulates  refrigerant  pressure  in  the  evaporator  to prevent  coil  freeze  up.    Valve  is  preset  to  establish  a minimum  pressure  of  57.8  psig  in  the  evaporator.    The back pressure regulating valve also bypasses refrigerant gas  from  the  discharge  line  to  the  suction  line  during bypass operation with the selector switch on "COOL". b.    Adjusting.    Remove  button  plug  from  the  back pressure regulating valve, (fig.  5-9),  loosen the lock nut at  the  top  of  the   valve   and   turn   the   adjusting   screw. Tighten the lock nut after adjustment and check  system operating pressures (para 6-14). c.    Removal.    Refer  to  figure  5-9,  and  remove  the back pressure regulator valve. Note.    Discharge  the  refrigerant  before  removing back pressure valve. d.    Installation.    Replace  a  defective  back  pressure regulating valve and install in reversing order of removal as illustrated on figure 5-9.  Test, evacuate and recharge refrigerant system (para 6-28, 29, 30). 6-21.  High and Low Pressure Cutout Switches a.        General.        The    high    pressure    cutout    switch prevents   the   compressor   from   operating   if   the   head pressure   exceeds   445   psig   (pounds   per   square   inch gage).      The   low   pressure   cutout   switch   prevents   the compressor  from  operating  if  the  suction  line  pressure drops below 7 psig. b.    Removal.    Discharge  the  refrigerant  system  and remove    high    and    low    pressure    cutout    switches    as illustrated in figure 5-10. c.  Testing.  Test the pressure switches for continuity across   the   connector   pins   with   a   multimeter   set   on OHMS.      If   no   continuity   is   indicated,   press   the   reset button and recheck. d.        Installation.        Replace    defective    pressure    cutout switches   in   reverse   order   of   removal   as   illustrated   in figure   5-10.      Test,   evacuate   and   recharge   the   unit refrigerant system (para 6-28, 29, 30). 6-22.  Pressure Relief Valve a.    General.    The  pressure  relief  valve  (fig.    5-12)  is located   on   a   cross   just   above   the   dehydrator.      The pressure relief valve protects the refrigerant system from excessive pressure.   It  is  preset  to  open  at  a  maximum pressure of 540 psig and is not adjustable. b.  Removal.  Discharge the refrigerant system, refer to figure 5-12, and remove the pressure relief valve. c.    Installation.    Replace  a  defective  pressure  relief valve   by   reversing   order   of   removal   as   illustrated   on figure   5-12.      Pressure   test,   evacuate   and   recharge refrigerating system (para 6-28, 29, 30). 6-23.  Evaporator Coil a.    General.    The  evaporator  coil  is  mounted  on  the casing, directly behind the discharge grille.  The coil must be    removed    from    the    air    conditioner    for    repair    or replacement.  The coil is made of brazed aluminum and is of the finned plate configuration. b.        Removal.        Refer    to    figure    5-5    and    remove evaporator coil. c.        Cleaning,    Inspection    and    Repair.        Refer    to paragraph 3-10 and clean and inspect the evaporator coil in a similar manner.  Inspect coil for bent fins, damaged coil  runs  and  internal  leaks.    Straighten  bent  fins  with needle   nose   pliers.      A   damaged   coil   or   an   internally leaking coil cannot be repaired. d.    Installation.    Replace  a  defective  evaporator  coil assembly   and   install   in   reverse   order   of   removal   as illustrated  in  figure  5-5.    Test,  evacuate  and  recharge refrigerating system (para 6-28, 29, 30). 6-24.  Condenser Coil a.        General.        The    condenser    coil    is    mounted horizontally  on  the  bottom  third  of  the  casing,  beneath the  air  filters.    The  coil  must  be  removed  from  the  air conditioner  for  repair  or  replacement.    The  coil  is  made from    brazed    aluminum    and    is    of    the    finned    plate configuration. b.      Removal.      Refer   to   figure   5-s3,   and   remove condenser coil. c.        Cleaning,    Inspection,    and    Repair.        Refer    to paragraph 3-11 and clean and inspect the condenser coil in a similar manner. 6-14

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