TM 5-6115-593-12 TO 35C2-3-463-1 ohms,    replace    the    transmitter.        Crank engine to determine that resistance decreases   to   approximately   70   ohms.      If resistance     does     not     decrease,     replace transmitter. b. Replacement.  (See figure 4-45.) (1)   Remove     nut,     washers,     and     lead     from transmitter threaded terminal. (2)   Unscrew transmitter from engine block. (3)   Install transmitter onto engine block. (4)   Reconnect   electrical   lead   using   nut   and washers. 4-73.  PRESSURE SWITCH.    (See  figure  4-40.)  There are three pressure switches labeled no.  1, 2, and 3 on figure 4-46. a. Inspection.        Inspect    pressure    switches    (see figure 4-46) for loose mounting, loose connection, dents, and leakage. b. Test OP1.  (See figure 4-46 and FO-3.) (1)   With generator set at shutdown and MAINTENANCE   LOCKOUT   switch   set   to OPERATION,    connect    miltimeter    (set    to measure DC volts) from terminal 26 of TB6 to   terminal   12   of   TB9;   multimeter   should read 24V DC. (2)   Crank engine and observe miltimeter; multimeter    reading    should    drop    to    zero almost immediately. c. Test OP2.  (See figure 4-46 and FO-3.) (1)   With generator set at shutdown, connect an ohmmeter (set to Rx1 scale) from terminal 7 to  terminal  12  of  TB22;  multimeter  reading should be less than 1 ohm. (2)   As    engine    is    being    cranked,    ohmmeter reading should jump to infinite ohms. d. Test OP3.  (See figure 4-46 and FO-3.) (1)   With   generator   set   at   shutdown,   connect ohmmeter from terminal 18 of TB20 to any convenient   ground   connection;   ohmmeter reading should be infinite ohms. (2)   Crank     engine     and     observe     ohmmeter; ohmmeter  reading  should  drop  to  less  than 1 ohm almost immediately. e. Replacement.  (See figure 4-46.) (1)   Disconnect leads from switch (1, 2, or 3). (2)   Unscrew switch (1 or 2) from engine block. (3)   For   reassembly,   screw   switch   into   engine block   and   tighten   to   20   foot-   pounds   (27 joules).  Reconnect leads to switch. 4-74.  OIL FILTERS.  (See figure 4-47.) a. Spin-on Type Filters.  Refer to paragraph 4-8 c for replacement of spin-on type oil filters. b. Bypass  Oil  Filters.    (See  figure  4-47.)  Inspect filter  case  for  dents,  cracks,  and  oil  leaks.    If damaged, refer to higher maintenance. 4-75.  SECONDARY FUEL FILTER ELEMENT. (See figure 4-40.) a. Service  and  replacement  of  the  secondary  fuel filter element is as follows (see figure 4-48). (1)   Unscrew   and   remove   the   filter   case   and discard filter element and gasket. (2)   Inspect  the  filter  case  for  dents  and  cracks that  affect  proper  sealing  when  reinstalled. If damaged, replace unit. (3)   Clean filter case.  Handle or store in manner to prevent out-of-round. (4)   Insert  new  element  in  filter  case  seating  it securely. 4-106