TM   9-2350-256-34-1 Replace the complete burner as an assembly if the plate and bushing assembly is defective. (9) Heat exchanger (fig. 3-10.2). (a) Inspect the heat exchanger (15) for leaks, cracks,  and  carbon  deposits.  The  interior  of  a  unit which has been burning leaded gasoline will contain a  deposit  of  lead  by-products.  Clean  the  heat  ex- changer  as  instructed  in  paragraph  3-34e. (b) Check  for  warping  of  inner  passages,  or bulging  of  the  heater  plate.  Replace  the  heat  ex- changer if warping  or bulging is excessive, or if any part  is  burned  through. (c) Small cracks may be repaired by welding, provided they are accessible and the heat exchanger is  otherwise  in  good  condition.  Do  not  attempt  to repair large cracks, or to straighten a deformed heat exchanger. WARNING Carefully inspect the heat exchanger, and repair or replace it if damaged. Exhaust gases  are  directed  through  the  heat  ex- changer.   These   gases   contain   carbon monoxide,   a   colorless,   odorless,   deadly poisonous gas. Cracks or holes in the heat exchanger  permit  the  exhaust  gases  to  en- ter  the  heated  compartment.  This  can result  in  the  serious  illness  or  death  of personnel  in  the  compartment.  Never take  chances  with  a  defective  heat  ex- changer. (d)  When  welding  cracks  in  the  heat  ex- changer,  Type  310  weld  rod  is  preferred,  although Type 349, 321, or 347 may be used. Before welding, it is very important to clean all combustion deposits away from the area to be welded, since deposits in the exchanger can contaminate the weld to such an extent that a tight weld is almost impossible. Keep weld beads as small as possible, preferably not over 1/8  inch. (10) Miscellaneous heater parts (fig. 3-10.2). (a)  Inspect  the  guard  assembly  (16)  for cracks,  dents,  distortion,  loose  or  defective fasteners,  and  other  damage;  replace  a  damaged guard assembly. (b) Inspect  the  secondary  blower  housing  (3) for  cracks,  distortion,  loose  weldments,  and  other damage;  replace  damaged  parts. (c) Inspect  the  heater  housing  assembly  (28) for   cracks,   dents,   distortion,   missing   weld   nuts, broken studs, broken weldments, and other damage; replace  a  damaged  housing. 3-36. Reassembly and Installation a.  Reassembly  of  Air  Control  Assembly.  Refer  to figure 3-10.1 and reassemble the air control assem- bly. b.  Personnel  Heater  Components. (1) Fuel control valve reassembly  (fig.  3-10.4). (a) Install  the  elbow  (11)  on  the  valve  body (18), and position it as shown in figure 3-10.8). (b)  If   the   thermostat   (17,   fig.   3-10.4)   was removed,  position  it  on  the  valve  body  and  secure with two screws (15). Install the wire (14), making sure the insulator (12) and insulating sleeve (13) are in place before soldering the wire to the heater and thermostat   terminals.   Solder   the   cable   assembly (16)  to  the  other  thermostat  terminal. (c) Install seal (36) on plunger (35) and insert valve  spring  (26)  in  the  plunger  assembly.  Insert assembled  spring  and  plunger  into  sleeve  and  core assembly  (28).  Position  gasket  (27)  and  sleeve  and core   assembly   (28)   on   valve   body,   and   install solenoid  cup  (29)  with  three  screws  (33)  to  retain part.  Repeat  to  install  plunger  assembly  (34)  on other  side. (d) Screw valve core (19) in valve body. Install new preformed packing (25) in recess in valve body. Install diaphragm assembly (24) and diaphragm cap (23). Fasten with four screws (20). Insert diaphragm spring (22) in adjusting screw (21) and install parts in  diaphragm  cap. CAUTION Do not attempt to replace the valve core (19)  with  an  automobile  tire  valve  core. Despite  their  similarity  of  appearance,  a tire  valve  has  not  been  designed  for  use with the fuels used in this heater, and will deteriorate rapidly if installed in the fuel control  valve  instead  of  valve  core  fur- nished  for  the  fuel  control  valve. (e) Install three small preformed packings (9) into  recesses  in  valve  body.  Set  restriction  orifice plate  (8)  and  3-hole  plate  (7)  in  place  and  install preformed  packing  (6).  Install  insulator  plate  (5)  and outer plate (4) and fasten with three screws (3). (f) Install washer (30) and coil assembly (31) in  restriction  solenoid  cup  and  fasten  with  screw (32). Repeat with the coil assembly (10) in the shut- off  solenoid  cup.  See  fig.  3-10.8  for  proper  orien- tation of these coils in the valve body. 3-18.16 Change 2