TM 9-4940-342-14&P Table 5-1.  Troubleshooting - Continued Malfunction Probable Causes Corrective Action 1.  Pump control switch closed, motor does not start-Continued e.  Defective stepdown tran- sformer - Continued Check red and black power leads for continuity.  Tighten  or  replace.  Low or   zero   voltage   across   transformer secondary    terminals    X1    and    X2 should    be    110-120V    AC.    Check terminals   at   transformer   secondary for  tightness.  Tighten  or  replace  as necessary.   Continuity   check   across primary  and  secondary  coils  indicate open coil. Replace transformer. f.  Motor single phasing. f.  Motor   will   emit   a   high   hysteresis hum   and   will   not   rotate.   Check   3 phase power supply conductors, motor,   disconnect   switch,   magnetic starter   for   shorts,   grounds   or   loose terminals.    Inspect    magnetic    starter heater elements for correct in- stallation   and   tightness.   Check   for dirty magnetic starter contacts. Repair  or  replace  damaged  parts  or conductors. g.  Wire loose, broken or shorted. g. Zero voltage at transformer primary. Check continuity of primary conductors. Replace or repair    as    necessary.    Zero    voltage between 115V control circuits 1 and 2 at    control    terminal    board.    Check continuity of control conductor. Replace  or  repair  as  necessary,  Zero voltage  between  115V  control  circuit 11  and  2  at  magnetic  starter.  Check continuity  of  the  control  circuits  11 and  2  conductors.  Replace  or  repair as necessary. h.  Defective motor start switch. h. Continuity check across switch shows    open    when    the    switch    is closed. Replace switch. i.  Magnetic starter coil defective. i.  Continuity    check    across    coil    in- dicates open. Replace the coil. j.  Motor mechanically bound. j.  Motor  shaft  does  not  rotate  by  hand. Repair or replace motor as necessary. 2.  Low fire switch closed, burner does not ignite. a.  Air pressure switch contacts open. a. Zero  voltage  between  115V  control circuits   3   and   2   at   control   circuit board.    Zero    voltage    between    NO contact  of  switch  and  control  circuit at terminal board. See malfunction 3. b.  Low water pressure switch contacts open. b. Same     as     step    a.     Zero     voltage between   M1   contact   of   switch   and control   circuit   2   at   terminal   board. Depress  switch  by-pass  push  button, if   burner   lights   contacts   are   open. See malfunction 4. c    Excess temperature switch contacts open. c. Same     as     step    a.     Zero     voltage between  NO  contact  of  switch  and control  circuit  2  at  terminal  board. See malfunction 5. d.  Low oil pressure switch contacts open. d. Same     as     step    a.    Zero     voltage between  M1  contact  of  switch  and control  circuit  2  at  terminal  board. See malfunction 6. 26