TM 9-2350-256-34-1 1  Remove   six   nuts   (1   and   2)   and   flat washers  (3)  from  studs  on  burner  cup  and  stud assembly  (14).  Remove  burner  cup  from  plate  and bushing  assembly  (6). 2  Remove   screw   (13)   and   pull   off   fuel vaporizer  shield  (12),  and  washers  (10  and  11). Detach yarn wick (5) from with support in plate and bushing  assembly  (4).  Remove  fuel  vaporizer  (9), retaining  washer  (8),  notched  washer  (6),  slotted washer (7), and second notched washer (6). (9) Heat exchanger (fig. 3-10.2). (a)  If   the   heat   exchanger   (15)   is   being removed  for  heater  overhaul,  remove  the  following components  to  facilitate  cleaning  of  the  heater housing: 1 Ignition  control  ((7)  above.  ) 2 Fuel control valve ((6) above). 3 Overheat switch ((5) above). 4 Electrical inlet assembly ((2) above). (b) Remove burner assembly ((8) above. (c)  Remove  the  flame  detector  switch  ((4) above). (d) Disconnect ground lead assembly (12, fig. 3-10.2)  from  heat  exchanger  (15)  by  removing  at- taching screw (11). (e) Remove  four  screws  (34)  holding  together the seam of the heater housing (28). Spread heater housing and slide out heat exchanger (15). (f)  Remove   the   ground   lead   (12)   from   the heater  housing  (28)  by  removing  the  nut  (14)  and lockwasher ( 13). (g) If  the  grommet  (33)  is  worn  or  damaged, remove  it  from  the  heater  housing. 3-34.  Cleaning WARNING Be careful when using cleaning solutions and   solvents.   Do   not   expose   skin   to solvents   or   inhale   their   vapors.   Many cleaning   agents   are   toxic,   and   contact with   them   or   their   vapors   may   cause illness or death. Wear protective clothing and  devices,  and  ensure  adequate  ven- tilation  while  using  cleaning  agents. a. Clean dirt and foreign matter from all exterior metal  parts  with  drycleaning  solvent  or  mineral spirits  paint  thinner  and  dry  with  compressed  air. b. Clean air inlet hose and rubber seals in a mild soap  solution,  rinse  and  dry. c. Clean the fuel filter in the inlet line to prevent the  collection  of  moisture  and  the  formation  of  ice during   cold   weather.   Follow   the   manufacturer’s recommendations. CAUTION Do  not  attempt  to  operate  the  heater without a fuel filter, or with the fuel filter 3-18.10 Change 2 element   removed.   The   filter   element prevents  the  entry  of  dirt,  ice  crystals, wax,  and  other  contaminants  which  can easily  plug  the  tiny  orifices  in  the  fuel control valve. d.  Clean  blower  housing,  ventilating  blower wheel,  combustion  blower  wheel,  secondary  blower cover  assembly,  motor  mounting  brackets,  and  ex- terior of motor with a cloth dampened with cleaning solvent. e. Clean the burner and heat exchanger. The bur- ner  has  been  designed  to  eliminate  excessive  buildup of carbon and other deposits within the combustion chamber.   However,   buildup   can   occur   under unusual operating conditions or if other components are malfunctioning. A minor carbon buildup may be removed by operating the heater at near maximum voltabe  and  restricting  outlet  airflow  to  maintain the temperature of the heat exchanger at or near an overheat  condition.  The  operate  the  heater  on  LO long enough to permit the excess combustion air to burn out soot and carbon. Repeat this cycle several times. (1) If this procedure faills to clean the heat ex- changer  enough  to  restore  performance,  or  if  the burner  or  heat  exchanger  require  further  service, remove  the  heat  exchanger  as  described  in paragraph  3-33c(9),  and  then  remove  as  much  of this  deposit  as  possible,  using  a  flexible  scraper. Remove  combustion  residue  from  inside  heat  ex- changer by soaking this assembly in a 20 percent by weight  solution  of  ammonium  acetate  at  a  tem- perature  of  1800  F.,  for  a  period  of  5  to  10  hours. Flush out exchanger with water after cleaning, and dry with compressed air. (2)  For  units  which  have  been  burning  other types  of  fuel,  such  as  diesel  fuel,  JP-4,  etc.,  water should  be  used  to  flush  the  heat  exchanger.  Use compressed  air  to  dry  the  inside  of  the  heat  ex- changer and remove all traces of water before heat exchanger  is  reinstalled  in  the  heater. f. Wipe all non-metallic parts of fuel control valve with a clean, dry cloth. Clean metallic parts except the   orifice   plate   with   a   cloth   dampened   with cleaning solvent. Take care not to saturate electrical windings  or  insulation  with  solvent.  Dry  all  parts thoroughly.   Clean   orifice   plate   holes   and   orifice plate  with  solvent  and  compressed  air.  Inspect  for cleanliness  with  a  magnifier. CAUTION Do  not  force  any  tool  or  object  through the  orifice  plate  openings.  The  slightest distortion  in  these  calibrated  holes  will change the factory calibrated flow. g. To  clean  the  flame  detector rate of fuel switch,  refer  to