CAUTION: The system must be completely empty
before opening any fitting or connection in the
refrigeration system. Open fittings with caution
even after the system has been emptied. If any
pressure is noticed as a fitting is loosened,
retighten fitting and evacuate the system again.
A good rule for the flexible hose lines is to keep
the radius of all bends at least 10 times the diame-
ter of the hose. Sharper bends will reduce the flow
of refrigerant. The flexible hose lines should be
routed so they are at least 3 inches (80 mm) from
the exhaust manifold. Inspect all flexible hose lines
to make sure they are in good condition and prop-
erly routed.
The use of correct wrenches when making con-
nections is very important. Improper wrenches or
improper use of wrenches can damage the fittings.
The internal parts of the A/C system will remain
stable as long as moisture-free refrigerant and
refrigerant oil is used. Abnormal amounts of dirt,
moisture or air can upset the chemical stability.
This may cause operational troubles or even seri-
ous damage if present in more than very small
quantities.
When opening a refrigeration system, have every-
thing you will need to repair the system ready. This
will minimize the amount of time the system must
be opened. Cap or plug all lines and fittings as
soon as they are opened. This will help prevent the
entrance of dirt and moisture. All new lines and
components should be capped or sealed until they
are ready to be used.
All tools, including the refrigerant dispensing
manifold, the manifold gauge set, and test hoses
should be kept clean and dry.
OPERATION
High pressures are produced in the system when it
is operating. Extreme care must be exercised to make
sure that all connections are pressure tight. Dirt and
moisture can enter the system when it is opened for
repair or replacement of lines or components. The
refrigerant oil will absorb moisture readily out of the
air. This moisture will convert into acids within a
closed system.
HVAC FORCED RECIRCULATION
DESCRIPTION
The HVAC system (both Manual A/C and ATC)
may force itself into recirculated airflow when
extremely hot outside ambient conditions exist. This
action can occur at a range of approximately 95°F to
120°F.
OPERATION
The Body Control Module (BCM) receives a Pro-
grammable Communications Interface (PCI) bus mes-
sage from the Powertrain Control Module (PCM)
with the feedback from the A/C Pressure Transducer.
The BCM will force the system into the Recirculation
mode, reducing the A/C refrigerant pressure under
these extreme conditions. The reduced operating
pressure offers improved A/C system performance
and reduced wear on A/C components.
REFRIGERANT LINES
DESCRIPTION
The air conditioning lines used on this vehicle are
made from reinforced rubber with a nylon liner on
the inner walls. The ends of the A/C lines are made
with light weight aluminum fittings.
CAUTION: Never attempt to disconnect an A/C line
without reclaiming all refrigerant from the air condi-
tioning system. The system must be empty.
OPERATION
The O-rings are made from a special type of rubber
that is not affected by R-134a refrigerant. O-ring
replacement is required whenever lines are removed
and installed. Use only O-rings specified for this
vehicle. Failure to use the correct type of O-ring will
cause the connection to leak within a short period of
time.
When it is necessary to open the refrigeration sys-
tem, have everything needed to service the system
ready. The system should not be left open any longer
than necessary. Cap or plug all lines and fittings as
soon as they are opened. This will prevent the
entrance of dirt and moisture into the system. All
new lines and components should be capped or sealed
until they are ready to be used.
WARNING: AVOID BREATHING A/C REFRIGERANT
AND LUBRICANT VAPOR OR MIST. EXPOSURE MAY
IRRITATE EYES, NOSE AND THROAT. USE ONLY
APPROVED SERVICE EQUIPMENT MEETING SAE
REQUIREMENTS TO DISCHARGE R-134a SYSTEM.
IF ACCIDENTAL SYSTEM DISCHARGE OCCURS,
VENTILATE WORK AREA BEFORE RESUMING SER-
VICE.
R-134a SERVICE EQUIPMENT OR VEHICLE A/C
SYSTEM SHOULD NOT BE PRESSURE TESTED OR
LEAK TESTED WITH COMPRESSED AIR. SOME
MIXTURES OF AIR/R-134a HAVE BEEN SHOWN TO
BE COMBUSTIBLE AT ELEVATED PRESSURES.
THESE MIXTURES ARE POTENTIALLY DANGER-
OUS AND MAY RESULT IN FIRE OR EXPLOSION
CAUSING INJURY OR PROPERTY DAMAGE.
LH HEATING AND AIR CONDITIONING 24 - 5
DESCRIPTION AND OPERATION (Continued)
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