TM  9-2350-256-34-1 3. Energize  the  power  supply  and  turn  on switch  A.  Adjust  power  supply  to  read  24  volts  at V,. 4.  Ground   the   voltage   limiter   on   test through its mounting bracket. Clip switch B to the flag  terminal. 5.  Turn   on   switch   B   and   observe   the volage on meter V2. The voltage must be 10.5 volts minimum to 11.5 volts maximum. NOTE The voltage limiter must act instantly to control the voltage at meter V2 and must remain steady at the control point. If the unit  is  left  energized  for  longer  than  60 seconds,   a   further   decline   in   control voltage  may  be  observed.  This  is  not cause for rejection. 6.  If   the   voltage   does   not   fall   within specifications, or if control is erratic or intermitent, voltage  limiter  must  be  replaced. 7. Turn  off  power  supply  and  switches  A and B. Remove voltage limiter from test equipment and  install  voltage  limiter  at  reassembly. (e) Test diode assembly as follows: 1. Identify the three diode assembly leads: a.  Lead  marked  4  with  connects  to  ter- minal 4 on terminal strip mounted on electrical inlet assembly. b.  Lead  marked  GRD  which  connects  to motor housing to ground the diode assembly. c.  Unmarked  lead  which  connects  to  one side  of  resistor. 2. Use  an  ohmmeter  or  ohms  test  function of  a  multitester.  Touch  one  test  probe  to  the  ter- minal  on  the  diode  assembly.  Touch  the  other  test probe  to  the  No.  4  lead  terminal.  Note  the  meter reading. Reverse the polarity of the test probes and note  the  meter  reading.  Resistance  must  be  very high with one polarity and zero or very low with the other   polarity. 3. Repeat this test with the unmarked lead. Results  must  be  the  same. 4. To  test  the  ground  diode,  touch  one  test lead  to  the  mounting  leg  of  the  diode  assembly. Touch  the  other  test  probe  to  the  GRD  lead  ter- minal. Note the meter reading. Reverse the polarity of   the   test   probes   and   note   the   meter   reading. Resistance must be very high with one polarity and zero or very low with the other polarity. 5. If readings are high or low in both direc- tions  for  one  or  more  of  the  diode  assembly  leads, replace  the  entire  diode  assembly.  Diodes  are  not serviceable individually. (2)  Electrical  inlet  assembly  (fig.  2-10.2).  In- spect  the  electrical  inlet  assembly  (36)  for  cracks, damaged   connector,   chipped   or   broken   terminal strip, missing  screws,    and  defective  fasteners; replace  a  defective  electrical  inlet  assembly. (3) Igniter (fig. 3-10.2) (a) With  the  igniter  leads  still  connected  to the ignition control and ground, reconnect the elec- trical cable to the receptacle and disconnect the fuel shutoff  solenoid  lead  from  terminal  30  on  the overheat switch (to shut off fuel and avoid flooding the burner), then move the control switch to START and  hold  it  until  igniter  element  glows. CAUTION If the igniter has been removed from the heater  it  must  be  tested  at  10  volts  or less.  Voltage  in  excess  of  10  volts  will destroy  the  igniter  in  a  short  time. (b) Carefully examine the glowing igniter. An igniter which has hot spots, uneven coil spacing, and hot  and  cool  coils,  has  deteriorated  significantly from its origiaal condition and should be replaced. (c) Ignition wick inspection. 1. With  the  igniter  removed,  look  into  the igniter tube and inspect the condition of the ignition wick (5, fig. 3–10.5) using a flashlight if necessary. The  wick  should  be  dry,  unbroken,  and  white  or nearly white. The strands should be about 1/16 inch thick. 2. If the strands are thin or broken, remove the   burner   assembly   as   described   in   paragraph 3-33c(8)  and  repair  or  replace  the  burner. 3. If the wick is wet, the burner is flooded. Disconnect the shutoff solenoid lead at terminal 30 on  the  overheat  switch.  Reinstall  the  igniter  and hold  the  control  switch  in  the  START  position  for several minutes. A white, smoke-like fuel vapor will flow from the exhaust until the heater lights. When the  heater  lights,  reconnect  the  shut-off  solenoid lead to terminal 30. (4) Flame detector switch (fig. 3-10.7). Change  2 3-18.13