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4.5
PREVENTIVE MAINTENANCE·
(Book
35386598,8/92)
AUTOMATIC SHUTDOWN SYSTEM
NOTICE
Do NOT wire around or bypass a shutdown
sensor or switch. Do not short-cIrcuit fuses.
The operation of
the automatic
shutdown
system
should
be
checked every month, or whenever
it appears not to be operating prop-
erly. The switches in this system
are listed in Section 3 on page 3.4.
The operation of these switches is
extremely important in order to pro-
tect the engine and the compressor
airend. The engine oil pressure
switch prevents the engine from
being damaged due to oil starva-
tion. Three switches help protect
the engine and compressor from
high temperatures.
Once a month remove a wire from
the engine oil pressure switch to
check the shutdown solenoid for
proper operation.
Once a year, the temperature
switches should be tested by re-
moving from the unit. The "fusible"
(non-resettable) switches can be
checked visually or with an ohm-
meter (0 ohms
=
good). The "reset-
table" switches must be tested with
an ohmmeter.
There should
ba
0 ohms between the wire
terminals. When the switch is
placed
in
the heated oil
bath
and its contact open,
the ohmmeter should indicate infinite
ohms.
The high discharge air temperature
switch
will
require
approximately
248°F (120°C)
10
actuate. The engine
coolant temperature switch
will
require
approximately 220° F (104°
CliO
actu-
ate. Replace any defective switch be-
fore continuing to operate the unit.
A low oil pressure switch
may
be
tested by removing it and connecting it
to a source of controlled pressure
while monitoring an ohmmeter con-
nected to the switch terminals. As
pressure Is applied slowly from the
controlled source, the switch should
close at 12 psi (80 kPa) and show con-
tinuity through the contacts. As the
pressure is slowty decreased to 8 psi
(55 kPa) the contacts should open and
the ohmmeter should' show lack of
continuity (infinite ohms) through the
contacts. Replace a defective
switcn
before continuing to operate the unit.
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