the  period  of  time  required  to  obtain  two  consecutive od) during a six-month period, it is water   temperature   readings   of   160°   F   minimum, recommended that the filters and lubri- taken  at  a  15-minute  interval.  Then  continue   to eating oil be changed (para 3-4). If operate   engine   for   30   minutes.   Check   and   correct any  coolant  or  oil  leaks. the accumulated hours of operation dur- ing the above exercise periods do not c. Stop engine as shown in figure total 100 hours (recommended fuel filter 2-8. If the accumulated hours of opera- change period) during a 12-month period, tion during the above exercise periods it is recommended that the fuel filter do not total 300 hours (recommended lube element be replaced (para 3-160). filters and lubricating oil change peri- Section V. OPERATION UNDER UNUSUAL CONDITIONS 2-16. Operation in Extreme Cold (Below- 25°F). a.  General.  The  engine  generator  set  is  designed to   operate   in   temperatures   down   to   -   25°F   without winterization   equipment.   To   operate   successfully   at temperatures   below   -25°   F,   the   engine   must   be   heated by   integrally   mounted   electric   winterization   heating equipment   (fig.   2-12)   which   receives   auxiliary   power from  an  external  source  or  by  a  fuel  burning  winteriza- tion   system   (fig.   2-11).   Operate   fuel   burning   winter- ization  system  for  55  minutes  or  until  fuel  burning winterization   system   cycles   off.   Operate   electric   win- terization   for   5   hrs. b .   Fuel   System.   Keep   the   fuel   tank   as   full   as   pos- sible   to   prevent   condensation   of   moisture.   Be   sure the   proper   grade   of   fuel   is   used   for   existing   tempera- tures. Service  the  fuel  filters  and  strainers  (para 3-34b)   more   frequently   than   normal.   Remove   ice, snow,   and   moisture   from   the   filler   cap   and   filler neck.   At   end   of   day’s   operation,   drain   water   from fuel  tank  (fig.  3-7)  and  from  the  fuel  filters  (para  3-56). c.   Engine   Electrical   System.   Clean   the   batteries and   cables   and   inspect   for   cracked   or   damaged   cases. Be  sure  the  battery  terminals  are  tight,  clean,  and lightly   greased.   See   that   the   battery   cap   vent   holes are   open. The   electrolyte   level   must   be   3/8   inch above  the  plates.  To  prevent  the  batteries  from  freez- ing,   see   that   they   are   kept   fully   charged.   Inspect   all electrical   wiring   for   cracks,   breaks,   and   fraying. Tighten   loose   connections. NOTE After   adding   water   to   the   batteries in   freezing   temperatures,   run   the engine  for  at  least  an  hour  to  thor- oughly  mix  the  water  with  the electrolyte. d .   Lubrication.   Lubricate   the   engine   generator   set in   accordance   with   instructions   in   paragraphs   3-3   and 3-4. e .   Cooli ng  System. Inspect  the  level  of  the  coolant in   the   radiator.   Inspect   the   cooling   system   for   leaks, aying   particular   attention   to   gaskets   and   hose   con- nections. Verify   that   antifreeze   mixture   is   in   ac- cordance   with   table   2-1. f.   Air   Cleaner.   Refer   to   paragraph   3-32   for   proper maintenance   of   air   cleaner. 2-17.  Operation  in  Extreme  Heat  (up  to  +  125°  F). a.   Keep   the   cooling   system   free   from   rust   and scale. If   necessary,   add   an   approved   rust   inhibitor. Keep   cooling   system   filled   with   clean,   approved coolant. Avoid,   if   possible,   the   use   of   alkaline   water or   salt   water,   which   cause   the   accumulation   of   rust and   scale. Inspect   the   belts   for   proper   adjustment. Be  sure  that  the  engine  generator  set  is  free  of  dust and   dirt.   Check   for   obstructions   in   the   cooling   fins of   the   radiator   and   make   sure   shutter   controls   are operating   properly. b.   Lubricate   the   engine   in   accordance   with   the instructions   in   paragraph   3-3   and   3-4. c.  Do  not  fill  the  fuel  tank  too  full;  allow  sufficient room  for  fuel  expansion. d .   Inspect   battery   electrolyte   level   daily.   The plates  should  be  covered  with  3/8  inch  of  water.  Add water  if  necessary. WARNING Exhaust  discharge  contains  nox- ious and deadly fumes. Do not operate generator sets in in- closed areas unless exhaust dis- charge is properly vented to the  outside. e. Check that the engine generator — set is free of air-flow restrictions. When  operating  indoors,  make  provisions for adequate ventilation and the vent- ing of exhaust fumes to the outside. TO prevent excessive back pressure, it is recommended  that  an  exhaust  extension of flexible tubing be no longer than 20 feet f. g. allow 2-18. (maximum). Keep   external   surface   of   engine   clean. The  unit  should  be  allowed  to  run  at  no  load  to the  engine  to  cool  prior  to  shutdown. Operation  in  Dusty  or  Sandy  Areas. Change 12 2-27