TM 9-4940-342-14&P (10)  When the RF relay is energized, contact RF-2     opens     and     the     LS     heater     circuit     is disconnected. Contact RF-3 opens and the ignition transformer  is  de-energized.  Contact  RF-4  closes and powers terminal 5. (11)  With terminal 5 energized, burner switch high  may  be  closed,  powering  the  high  fire  fuel valve through control circuit no. 6. (12)  In the event flame is not detected within 12  seconds  after  TD  relay  is  energized,  the  LS heater  will  trip  the  lockout  switch  opening  LS-1, which  disconnects  power  to  terminal  8,  all  load terminals  and  TD-2.  LS-2  closes  and  terminal  A (alarm)   is   energized.   The   flame   failure   light   is powered   through   control   circuit   no.   8.   Before restart,  the  lockout  switch  (red  reset  button)  will have to be reset. (13)  In   the   event   of   flame   failure,   fuel   is interrupted   within   two   seconds.   Ignition   is   not brought  back  on  until  after  a  new  seven-second prepurge   cycle.   If   the   low   fire   flame   fails   to reignite, lockout will occur in 12 seconds. (14)  In   the   event   that   the   flame   relay   is energized  (flame  detected)  at  any  time  during  the prepurge,  RF-1  will  close  and  by-pass  the  time delay network, bringing it back to 0 seconds, where the   timing   stops   until   the   flame   relay   is   de- energized. (15)  If  the  flame  relay  should  remain  in  an energized position, RF-5 will be closed and the LS heater  will  be  powered  through  RF-5  and  TD-3. Lockout will occur in 12 seconds. (16)  If,  during  normal  operating  conditions, any of the limit switches open, terminal no. 7 will be  de-energized.  The  TD  relay  will  de-energized and contact TD-2 will open, closing the fuel valves. After  condition  which  opened  the  limit  switch  is rectified, a new seven-second prepurge is required before the low fire fuel solenoid valve and ignition transformer is powered. NOTE During normal modulation of the burner, the fuel low pressure switch will open causing recycling of the burner. (17)  If  the  above  sequences  do  not  occur  in the   manner   listed   and   the   difficulty   has   been isolated to the UV scanner and relay, first test for continuity   across   the   scanner   leads.   If   scanner shows open, replace scanner. (18)  If scanner is functional, inspect relay for mechanically bound flame relay or time delay relay (refer  to  fig  4-2).  Inspect  relay  contact  blocks  and observe   if   blocks   are   cocked   on   guides.   Free contact   block   and   assure   block   moves   contact freely. (19)  Inspect relay for broken or loose conductors,  broken  solder  joints  or  broken  or  loose terminals. Repair as necessary. (20)  If   difficulty   cannot   be   isolated   by   the preceding steps, the relay should be replaced. 6-6. Coil Inlet Assembly (Refer to Fig C-14) All fittings and components should be inspected and replaced  if  found  to  be  defective.  No  attempts  shall be   made   to   patch,   plug,   solder   or   weld   leaking fittings. 6-7. Burner Plate Assembly (Refer to Fig C-16) The  burner  plate  weld  assembly  may  be  repaired when  utilizing  normal  welding  procedures  for  equal or  similar  components.  Plate  assembly  shall  require removal of all components prior to welding or other major repairs. Major damage is cause for replacement. 6-8. Outlet Coil Assembly (Refer to Fig C-17) All fittings and components should be inspected and replaced   if   found   defective.   For   replacement   of valves only, these fittings requiring removal shall be disassembled from assembly. Always start disassembly sequence at component being repaired to minimize fitting removal. No attempts shall be made to  patch,  plug,  solder  or  weld  leaking  fittings  for distort fittings for forced installation. 6-9. Outlet Assembly Soap Tank (Refer to Fig C- 31) A   defective   valve   is   cause   for   rejection   and   no attempts to repair it shall be made. 6-10.  Air Dome Outlet Assembly (Refer to Fig C- 25) All   fittings   should   be   inspected   for   defects   and replaced if found defective. 6-11.  Wheel Assembly Blower (Refer to Fig C-26) The wheel assembly blower may be disassembled for component part replacement only. No attempts shall be made to weld, peen or patch blower plate casting. Blower cage is not repairable and must be replaced if inspection reveals defects. 6-12.  Switch Assembly and Breaker (refer to Fig C-28) a.  Remove   magnetic   starter   contact   block   and inspect   contacts   for   cleanliness.   If   contacts   have carbon  deposits,  clean  with  burnishing  tool  or  fine crocus cloth. b.  Remove  magnetic  coil,  test  continuity  across coil. If coil shows open, replace. c.  Check   ratchet   wheels   on   thermal   overload 48