PIPER
SENECA
II
SERVICE
MANUAL
NOTE
The air conditioning system should be operated
at
least once a
month
to
prevent sticking valves and keep the system lubricated.
14-96.
MALFUNCTION DETECTION. The detection
of
system malfunction largely depends on the
mechanic's ability
to
interpret the gauge pressure readings into system problems. A system operating
normally will have a low side gauge pressure reading that will correspond with the temperature
of
the
refrigerant evaporating in the evaporator, allowing for a
few
degrees temperature rise due to loss in the tube
walls and fins. The high side will have a gauge pressure that will correspond with the temperature
of
the
refrigerant condensing in the condenser, allowing for a few degrees temperature drop due
to
loss in the tube
walls and fins.
Any deviation from that which is normal indicates a malfunction within the system due
to
a faulty
control device, obstruction, defective part,
or
improper installation.
Detection
of
system malfunction is made easier with the knowledge that the temperature and pressure
of
Refrigerant 12 is in close proximity between the pressures
of
twenty and eighty pounds per square inch
(psi). A glance
at
the temperature-pressure chart will show that there is only a slight variation between the
temperature and pressure
of
the refrigerant in the lower range.
It
is
correct
to
assume that for every pound
of
pressure added
to
the low side, a temperature increase
of
about one degree Fahrenheit takes place.
For
instance, a pressure
of
23.8 on the chart indicates a
temperature
of
24°F. A change
of
pressure
of
almost one pound
to
24.6 psi
gives
us
a temperature increase
to
25°F.
NOTE
For
each 1,000 feet
of
elevation above
sea
level, the
gauge
readings
will be about one inch
of
mercury
or
1
/2
psi higher than the chart
indicates.
It
must be pointed out that the actual temperature
of
the air passing over the coils
of
the evaporator
will be several qegrees warmer allowing for a temperature rise caused by the loss
in.
the fins and tubing
of
the evaporator.
The importance
of
a seasonal check up
of
the air conditioning system should be brought to the
attention
of
the customer whenever possible. A thorough check
of
the system performed in a methodical
manner will reveal trouble the customer
is
often
not
aware of. Locating and repairing the trouble early will
usually result in savings
to
the customer
both
in time and additional troubles that too often result from
neglect.
A Performance Test
of
the system
is
the only positive way in which the complete system can
be
checked for efficient operation. The air conditioning system should be
given
this test before work
is
begun
on the system whenever possible, however,
if
the system is completely inoperative, repairs must be
performed before the system can be properly tested. The test can uncover further work
that
must
be
performed before the system
is
brought
to
its full operating efficiency. The Performance Test should always
be performed after repair work has been done and before the aircraft is released
to
the customer. The
serviceman performing this test carefully will insure that the repairs have been properly performed and that
the system will operate satisfactorily.
The Performance Test when properly performed includes a thorough examination of the outside
of
the system
as
well
as
the inside. Many related parts are overlooked because
it
is felt they are
of
no bearing
on the operating efficiency
of
the unit.
For
this reason, a thorough visual inspection
of
the complete system
should be performed, followed by an operating inspection
of
the system.
Reissued:
10/11/79
3D2
ACCESSORIES
AND
UTILITIES
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