Section 2
DESCRIPTION
14
Figure 2 --- 5 Air Inlet System --- John Deere
the inlet valve remains fully open for maximum air
output. The engine will continue to run at full speed
during this phase of operation.
MODULATION --- 100 TO 110 PSIG (6.9 TO 7.6
BAR) OR 150 TO 165 PSIG (10.3 TO 11.4 BAR)
FOR “H” MACHINES
Should less than the rated capacity of air be used,
theservice line pressure will riseabove100psig(6.9
bar) low or single pressure rating, 150 psig (10.3
bar) dual or high pressure rating. The pressure reg-
ulating valve gradually opens, applying pressure to
the inlet valve piston and speed control cylinder.
This causes the inlet valve to partially close and re-
duces the speed of the engine. As the pressure in-
creases, the inlet valve piston will further close the
inlet valve and continue reducing the speed until it
reaches a pre---set idle speed. Now as air demand
increases, the sump pressure will fall below the 110
psig (7.6 bar) or 165 psig (11.4 bar) for “H” ma-
chines.
The pressure regulating valve will close, the air inlet
valve will fully open and the engine will once again
run at a pre --- set full load speed.
Between the pressure regulating valve and inlet
valve, a small orifice is installed which vents a small
amount ofair to the atmosphere, when the pressure
regulating valve is open. This allows variance of air
output to match air demand. The orificealso bleeds
any accumulated moisture from the regulator.
SHUTDOWN
The blowdown valve is normally closed. Upon shut-
down, the back pressure in the compressor inlet
signals the blowdown valve to vent the sump pres-
sure to the atmosphere. After the sump pressure
hasvented,theidlewarm---upvalvewillautomati-
cally reset from normal operation mode to start
mode.
2.7 AIR INLET SYSTEM, FUNCTIONAL DESCRIP-
TION
Ref er to Figur e 2 --- 5 . The a ir inl et s ystem c onsists of
two air filters
,a
compressor air inlet valve
and
in-
terconnecting piping
to the engine and compres-
sor.
The air filters are 2---stage dry element---type filters.
These filters are capable of cleaning extremely dirty
air. However, in such cases, frequent checks of the
air filter will be required.
S ee S ec tion 5 f or A ir Fil ter M aintenanc e Pr oc edur es.
2.8 INSTRUMENT PANEL GROUP, FUNCTIONAL DE-
SCRIPTION
Refer to Figur e 2 --- 6 . The instr ument panel gr oup
consists of a heavy gauge panel containing an
air
pressure gauge, hourmeter, starter pushbutton,
toggle ignition switch, circuit override button,
cold weather starting aid button (Caterpillar
only), circuit breaker, warning light
for
alternator
malfunction,
and
idle warm --- up b utton
.A
high ---
low pressure selector switch
is located on the
panel for 185H compressors.
Refer to Figur e 2 --- 6 f or l oc a tions of the fol l owing in -
dicators and controls:
S
The
air pressure gauge
continually monitors the
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