compressor unit should load at a minimum  pressure  of 2,300  psig  (  1  5847  kPa).    Air  compressor  unit  should unload   at   a   maximum   pressure   of   3,300   ±   50   psig (22,392 kPa).  If air compressor loads or unloads at an incorrect    pressure,    refer    to    PRESSURE    SWITCH ADJUSTMENT (Section V). k. Push  ENGINE  THROTTLE  CONTROL  to the  idle  position.    Disengage  clutch  by  pulling  CLUTCH operating rod away from control panel. l. Allow  engine  to  run  without  a   load   at   a maximum    speed    of    1,400    rpm    (1,400    r/min)    for approximately five minutes. m. Push    ENGINE    TIHROTTLE    CONTROL completely in.  Turn MASTER SWITCH 45° ccw. n. To  drain  the  air  from    the  air  compressor system,    open    the    DEHYDRATOR    BLEED    VALVE, mechanical filter drain valve (II), and service hose bleed valve (13). 5-3. Pressure  Switch  Adjustment  (Figure  5-1).    The pressure  switch  is  located  in  the  unloader  control  box (Figure  1-1).    Unfasten  and  raise  cover  of  control  box. To  adjust  pressure  switch  actuating  point,  proceed  as follows: Figure 5-1.  Pressure Switch Adjustment a. Observe compressor pressure gauge indication     when     compressor     unloads.          The     air compressor unit should unload at 3300 ± 100 psi (22,757 ± 689 kPa). b. Using    an    open    end    wrench,    or    offset screwdriver, turn adjusting screw clockwise to decrease switch    actuating    pressure    and    counterclockwise    to increase switch actuating, pressure. c. Observe     service     pressure     gauge (4) indication.    With  air  compressor  unit  operating  under normal   conditions,   compressor   unit   should   load   at   a minimum  pressure  of  3,000  psi  (20,670  kPa).    The  air compressor unit should unload at  a  maximum  pressure of 3300 psi ± 50 psi. 5-4. INSPECTION AND PREVENTIVE MAINTENANCE. Preventive maintenance checks, services, and inspection  are  listed  in  Table  5-2.    Detailed  procedures are contained in following paragraphs.  The table lists the service time in intervals of operating hours.  If a check, service, or inspection procedure should be accomplished at an interval other than operating hours, the time interval is listed in the service column. 5-5. Air   Compressor   Air   Filter   (Figure   5-2).      The compressor  air  cleaner  is  a  dry,  replaceable  element type.  Service the air cleaner as follows: a. Unscrew    the    winged    nut    on    the    top assembly.  Remove the top cover and filter element. b. If inside of  filter  can  is  dirty,  clean  with  lint free cloth. c. Install cleaned or new element on filter can base,  install  filter  cover,  with  the  air  inlet  hole  pointing away from the compressor.  Screw wing nut down finger tight. 5-6. Engine  Air  Filter  (Figure  5-3).    The  engine  air filter is an oil bath type.  Service the air filter as follows: a. Remove supporting band front air cleaner. b. Unfasten and remove oil container from air filter housing. c. If   oil   is   dirty,   dump   oil   and   dirt   from container. d. Clean container with a lint-free cloth using a hot water and detergent solution per Federal Specification, P-D-220.  Allow oil container to air dry. 5-2